As a vampire, she wears a small Lapis Lazuli daylight ring enchanted by Emmett Bennett, as a means to walk around in the sunlight as a vampire. The ring has the Salvatore crest and an embedded "D".
In flashbacks, as a human in the 1860's era, Danielle generally wore the same attire as her younger sister; Stephanie Salvatore, including dresses of beautiful colors, waistcoats, dress coats, hats, scarfs and leather laced boots as her usual style. Her color scheme as a human was much lighter, Danielle was seen wearing a red waistcoat, yet still formal, showing the Salvatore family's wealth. Her hair was slightly longer in style, with wild yet tamed curls, showing a much more youthful appearance.
- "You know, I used to miss being human. Now I can't think of anything more miserable on earth."
- — Danielle to Eli
Danielle was originally a very free-spirited young woman, who was best friends with her younger sister Stephanie Salvatore, both of whom were instantly smitten with the vampire Charlie Petrova. She had a positive relationship with Stephanie and she held her position as elder sister in high regard, being the one to teach Stephanie how to fight when they were younger. As a human, Danielle also held a sense of duty as she enrolled in the confederacy as a nurse, however their mother saw her as very irresponsible and reckless, proving she was very much a free spirit who did things on a whim, taking no mind to what people thought.
Danielle could be considered much the opposite to her sister in many regards. Whilst they both were respectful and polite, Danielle had a dark side which came to play when she fell in love with Charlie, whilst initially terrified at the prospect, her love for Charlie and dependency for his affections made the choice easy and she willingly drank his blood and conspired with him to kill innocent humans, a trait which passed on to his vampire lifestyle. Danielle was very naive as a human, she loved Charlie deeply and recklessly, regardless of the consequences and not caring that her mother was ashamed of her. Her carefree life fell apart when Stephanie betrayed Danielle by alluding to their mother that Charlie was a vampire; information that resulted in Charlie being trapped and taken to a church to be burned, also doing whatever she could to get him back, even if it resulted in her death.
- "And you know what makes me able to drink my fill and leave someone breathing and not rip their head off like my sister; is that I can revel in it. I can make it fun."
- — Danielle to Brax and Eli
- "I want to go back in time and fix every awful thing I've done… But I can’t take any of that back."
- — Danielle in 500 Years of Solitude
After she became a vampire, she left Stephanie's side, wanting no part in the life of the woman who betrayed her. She selfishly kept the fact that Charlie was still alive from Stephanie, jealous that her sister had also been turned by their shared lover. By the time she appears in season one, she's been away from Stephanie for at least eighty years (including the meeting in 1912), and she immediately begins taunting her sister, as a colder, more calloused version of her human self.
Throughout season one, Danielle acts arrogant and sarcastic, showing little to no regard for human life and using whatever people she can get her hands on as her personal playthings. She shows pity to neither Christian Forbes nor Victor Donovan, even going so far as to kill Stephanie's cheerleader coach to "prove" that she has no humanity left. She is also portrayed as a very impulsive vampire, known for her self-destructive behavior and her devious, sadistic mind. Despite this, she stays focused on her only goal: getting Charlie out of the tomb. This shows her ability for planning and forethought, and certainly the patience to wait one hundred and forty-five years for the necessary comet to return.
After Charlie is discovered to have been alive the entire time, and her reason for doing the things she has been doing shattered, Danielle becomes more dangerous because she drinks alcohol constantly, bonding with others at the bar. She destructively taunts Alanna Saltzman about being the one to kill her husband, Isobel Flemming, but is confused when she finds that Isobel is Eli's biological father. She tempts her sister with human blood, though she knows exactly what Stephanie used to be, and when Stephanie goes off the deep end, Danielle helps Eli detox her. She also genuinely thanks Brax Bennett for disabling the device that could kill her, surprising him with her sincerity.
Every time her sister is put in a situation that endangers her life, Danielle protects her, but she's not afraid to cause Stephanie non-lethal harm. Despite her anger with Stephanie for her actions in the past, she hangs around, protecting her and working with her, sometimes destroying the good in her life. Their perplexing relationship seems to center around Eli, who anchors them to Mystic Falls.
Eli is the oddity of Danielle's behavior, the anomaly that makes her personality far from psychopathic. In the beginning of the first season, Stephanie is prepared to give up on her sister, believing her to be an irreparable monster, but Danielle displays true feeling for Eli. Eli Gilbert is physically identical to Charlie, the man who turned her into a vampire, making him not only a constant reminder of what happened to her and Stephanie, but a temptation to let history repeat itself. When Charlie reveals that he never loved her (in the beginning of season two), Danielle reacts by trying to get Eli to admit that he loves her, and when he tells her that he loves Stephanie, she reacts impulsively, set off by both Charlie and Eli choosing her sister instead of her. She kills Eli's sister, spending many weeks afterwards trying to make it up to Eli, showing true regret for her actions. Their relationship began with taunting and cruelty, but he became what she clings to for humanity; she became his occasional protector, a guardian of sorts. Her impulsive actions often drive him away but he refuses to let her die, and she does the same for him.
With Eli influencing her throughout the second and third seasons, Danielle becomes slightly kinder, if only for the fact that she no longer mindlessly kills and torments humans without good reason, and she controls herself to be strong for Eli's sake. She proves that she is capable of love, nobility, loyalty, and selflessness, masking the most intense of her emotions to spare herself from seeming weak, but expressing just enough to draw in a very small circle of friends (which she later drives away). She continues to claim that her emotions can be turned off, but several older vampires reveal that this is a lie; after a certain amount of time, a vampire has to pretend they can't feel. The only time Danielle had ever admitted her pain was when Eli told her that he would never kiss her back, to which she responded, “Now I'm hurt.”
About halfway through the third season, Danielle believes that Eli is trying to turn her into Stephanie by constantly telling her to be the 'better woman.' Others continue to underestimate her and, to display that she doesn't care at all, she kills Alanna, with whom she'd developed a strong friendship. She also spends time trying to make it up to Alanna after her ring brings her back to life, treating her like a friend even though Alanna is extremely angry with her. She also snaps and feeds from Christian's mother, and, after a very violent fight with Christian, she is confronted by Eli. She's even cruel to him, accusing him of trying to make her into something she's not. Her inner turmoil continues when Charlie reappears, and she recklessly takes him offer of a 'road trip,' leaving Eli defenseless only because she is mad at him. When she returns, she displays genuine regret and, in one of her most tell-all, modest moments of the show, she tells him that she will never leave him again, showing her extreme love and devotion to Eli, and her regret for making another impulsive decision.
- "I just have to say it once; you just need to hear it. I love you, Eli... and it's because I love you that I can't be selfish with you. Why, you can't know this. I don't deserve you... but my sister does. God, I wish you didn't have to forget this... but you do..."
- —Danielle to Eli
She compels him to forget that she said this (late in season two), because she believes it would be selfish to confuse Eli with her feelings. This is right after Stephanie apologizes for making Danielle turn in 1864, something that surprises Danielle to the point of revelation: She realizes what she's been doing to her sister, all following one stupid mistake. In reality, what Danielle said to Eli proves that he has been molding her into a better person, because before that moment, she never would've done something so selfless. Danielle also admits to missing her human life before she drunkenly kills Jesse Cohen in the middle of the road; this secret is kept from everyone around her. She lets the boy go, but immediately chases him down and kills him anyway in an effort to prove that she doesn't really care. When her spirits are down, Danielle solves her problems with alcohol (mostly bourbon), but she often uses violence and murder to console herself.
By her own testimony, Danielle claims that the reason why she can control her vampiric urges is because she embraces what she is.
Danielle is also very self-confident, given that she'll confront older, stronger vampires like: Alex, Andy, Peter, Elisha, Nicole Mikaelson, Robert, Chloe, Charlie, Rufus and Selene. Without hesitation, and without regard to manners, even when they themselves pose no signs of hostility towards her. She often taunts them, which results in her nearly being killed quite often as they are undeniably stronger than her; though of course, there were cases when she was able to best them on some occasions, as in the case of Chloe and Selene. Further into season 4, Danielle seems to have lost part of her authoritative and dominating personality, most likely because of Nicole, who is much stronger, older and more powerful than her.
Despite Eli's influence, it seems that she is a very vengeful person and it is routed in her core. After the torture her and Luci experienced in the 1950's, she continued to carry out the revenge she swore to take even well into her and Eli's relationship. This also proves her to be very secretive, as she told nobody of her experiences, not even Stephanie in the aftermath of the torture until it was revealed in the present.
When Danielle fed on Joey in Total Eclipse of the Heart, she was shown to have no remorse or guilt over ripping the young vampire's head off.
In No Exit, Danielle appears to have much increased strength when she feels the urge to feed on Vampire blood, she has all the abilities that a normal vampire would have except, enhanced to much more extreme levels making her much more powerful than vampires that are much older than her. For example Danielle was able to break free from her chains in a matter of seconds when Luci chained her up. Though this is something any-other vampire might not be able to do.