Alexandra (Alex) Udinov is one of the main characters of Nikita. In the Pilot episode, she is seen robbing a drug store with her boyfriend Robbie. Robbie shoots the owner of the store and runs, so that the police catch Alex and place her in jail for this crime. Soon after Michael sees her being brought into prison and instead recruits her to Division.
Amanda originally thinks that Alex is Ukranian and asks the meaning of her butterfly tattoo, yet Alex is originally from Russia. She came illegally to America in a shipping container, alongside other immigrants, such asIrina. Nikita found Alex and saw potential in her to take down Division. Alex was a Division field agent and was making contact with Nikita outside of Division. She became good friends with Nathan, her neighbor, and as the latter half of Season One progresses they start a romantic relationship.
Alex is the daughter of the late exiled Russian oligarch Nikolai Udinov and his wife who were murdered when Alex was a child. Nikolai owned the billion-dollar company Zetrov, which Alex was the sole heir of. She was saved by Nikita as she watched the rest of her family perish. Nikita was powerless to save Alex from anything else as she had to return to Division, and Alex was sold into sex slavery at her very young age by one of her father's former associates.
To keep her from fighting against them, the slavers keep Alex with them by keeping her high and eventually forcing her to become a drug addict. For a few years, she has no choice but to stay with them to get her next fix. Nikita later resces her, as she tried years before, and forces her to become clean, but to Alex's irritation.
Alex brings this up to Amanda, saying that the slavers "had the decency to keep [her] high" as they held her captive, comparing this to Division. She also suffers panic attacks due to certain things that trigger somewhat supressed memories of her past, such as being under a car reminding her of being under a car as she watched her family die.
After Nikita succeeds in helping Alex past the worst part of her addiction, she starts to train her both mentally and physically to be fit enough and intelligent enough to stay one step ahead of Division when she is inserted there.
In her relationship with Nikita, the two shared the same ideals to bring down Division from the inside until the episode Betrayals. Nikita is a former recruit and the only one (at the start of the first season) to have escaped. Nikita attempted to rescue Alex after Nikita killed Alex's father, yet failed to stop the girl from being sold into human trafficking. Nikita does, however, help Alex by rescuing her from the traffickers and helping her become clean, despite Alex's protests. Alex learned of Nikita's plans and pledged to help avenge her family's murderers.
As of the end of Season One, Alex refuses to run off with Nikita and Michael, instead forging her own path. She shoots Nikita for the Division cameras, but it is revealed that she has shot her with a drug that stops vital signs but does not kill. Nikita quickly awoke when Roan was about to "clean" her body. Alex is not completely hostile towards Nikita, yet does not want to help her anymore. It is known that Alex will search for Nikita and Michael in Season Two.
Nathan Colville is Alex's neighbor as of the episode "Free". He initially invites her to a party he is holding in his apartment, at which Alex accidentally defends herself by "beating down" partygoer. The two become good friends, and he urges her to tell him of her real life and career after an odd dinner with Michael. Nikita spots signs of Alex and Nathan's relationship beginning to take a romantic turn, and she warns Alex that Division will know if she proceeds. Regardless, Alex and Nathan begin their relationship.
In Echoes, Alex runs into a part of her dream that she has imagined in her own apartment. She is searching for the younger version of herself she has been trying to protect throughout her dream, yet finds that, in this scenario, she and Nathan are married with a young daughter. Towards the end of her dream, Alex must fight a version of herself that she is scared to become, the Udinov heiress, from shooting her two potential family memebers.
Both Alex and Thom were new recruits at Division when Alex arrived, yet with Thom having been there longer than Alex. Due to Alex's almost instantaneous rivalry with Jaden, Thom and Alex grew close. This eventually blossomed into a romantic relationship as Thom finished his training as recruit. Alex was forced to kill Thom to prevent herself as being revealed as Nikita's mole.
Jaden was Alex's rival at Division before her death. Even though the two had paired up (such as when Alex needs to find the number for Michael's tracking device for Nikita from Division's doctor's computer, and their mission in "Girl's Best Friend") when they have needed a favor from one another, the two tended to be quite hostile when near each other, although this had cooled down since the start of the first season. In Echoes it was evident that Alex was terrified that she may eventually kill Jaden, even on purpose. This actually happens in Betrayals, when Jaden learns that Alex has told Nathan of their real lives, and she tries to kill Alex.
Irina is a girl from Alex's past whom is stuck in life that Alex, with the help of Nikita, managed to escape. Irina is a drug addict and a sex slave, both things that Nikita saved Alex from. Alex and Irina smuggled themselves into America together in the same containers.
Alex's relationship with Michael largely echoes that of Nikita's when she first met him, although rather noticeably without the romantic element. It was heavily implied before Echoes that Michael has figured out that Alex is Nikita's mole, and even does not say so when Thom is killed and blamed for this. Alex was highly suspicious of his and NIkita's relationship, and was not surprised when she imagined them kissing in Echoes.