Older identical twin. Sofia hated being mistaken for Alex thoroughout childhood and strived to be opposite to her. Where Alex was a tomboy, Sofia was a girly girl. Except for the time the girls spent with their father. After their 'deaths', Sofia closed off emotionally, putting on a mask. Years later, she finds her twin and mother at the Udinov Mansion during Alex's mission to kill Sergei and Nikita's mission to get the blackbox from Ari. When Alex is wounded, Sofia stays with her and is heartbroken by her mother's admission about her affair with Sergei.
Sofia was, like Alex, closer to their father. She had a complicated relationship with her mother. Whenever Katya pushed, Sofia pulled and visa versa. After the 'death' of her family, Sofia closed off and never forgave herself for not working things out with Katya. Years later, she finds Alex and Katya at the Udinov Mansion while trying to get a blackbox with Nikita.
When Sofia met Ryan after Nikita and Michael traded Percy for him. From the moment she meets him, Sofia refers to him as 'Tom Cruise', 'Ethan Hunt' and 'Mission Impossible', due to him looking similiar to the actor. She stays behind with Ryan and Birkhoff to oversee the meet that Nikita was using as a front to assassinate Morgan Kendrick. Using an unsecure wi-fi line to help deactivate Kendrick's kill chip, the group; Alex, Sofia, Ryan, Sean and Birkhoff were tracked down by Division and they escaped by blowing up the house. In the middle of Sean and Alex, Sofia was asked by Sean to lean forward and was uncomfortable at being inbetween her sister and Sean as they kissed. When Ryan found it awkward too, Birkhoff told him not to say anything and Sofia moves into the front and sits on Ryan's lap to avoid saying anything. The next time Sofia is seen with Ryan, it is at the White House during Percy's attack. In the finale, Birkhoff tells her of Roan's whereabouts and she tells Ryan she is going to help Sean and Alex. Before she leaves, Ryan kisses her and tells her not to get hurt. Later on, Sofia wakes up after her fight with Roan and getting electrocuted to hear Ryan is the new New Division leader. During season three, Ryan and Sofia have a secret relationship before it comes out and Ryan proposes. At first, Sofia is unsure because she feels she is broken inside. During an interrogation, Sofia blurts out that she believes she is broken because she feels nothing when killing but there is a flashback to a night with Ryan when he says he loves her but says he would wait for her to say it back because he knows it wouldn't be as easy for her so she says 'I love you' in Russian. Ryan asks what it meant but Sofia refuses to tell him. Back in her room, Alex and the group ask her why she feels she is broken, but she refuses to talk but then Owen guesses it was because the night she last said 'I love you' to someone, they were killed. Her father. Alex sees a way to get through to her sister and tells her she loves her but if she doesn't say it back, Alex would shot Ryan. This makes Sofia nervous and as Alex holds a gun to Ryan, Sofia puts herself between the gun and Ryan. Alex points out that only someone who was in love would do this, Sofia comes to a realisation that she isn't broken and kisses Ryan, telling him 'yes'. A couple of episodes later, she is married to him. When they return to work, Alex shoots Ryan and Sofia is by his side until duty calls.