Resident Evil 2
Annette Birkin was a research assistant to William before the two got married. Before the outbreak caused by James Marcus, William and Annette were very loving parents to their daughter Sherry. After William almost lost his life escaping the facility, he became extremely paranoid and obsessed with his creation of the G-Virus, making it his life's work.
Having helped her husband in the creation of the G-Virus, extracted from Lisa Trevor, she too became obsessed with the completion of the G-virus and began to ignore Sherry. William's paranoia rubbed off on Annette who became very suspicious of a woman snooping around Raccoon City trying to find out more about Umbrella and the G-Virus. Annette finds out that the woman, Ada Wong, is in fact a spy working for a rival pharmaceutical company and is trying to get a sample of the G-Virus.
Toward the end of the G-Virus development, William birkin decided to sell the virus to the US government. Umbrella not being happy about his decision sends out a Special Ops Team lead by H.U.N.K. to retrieve the virus samples. Not willing to give up his life's work, Birkin refuses and is shot down by the team. Birkin then injects himself with a sample of the G-Virus in order to avoid dying. William then transforms into a mindless monster fit on destroying everything in his path and procreating. A G-Virus subject is compatible with anyone of the same gene type such as sibling, parent, or offspring and is drawn to them.
Annette locates Ada in the sewers and opens fire on the agent. Leon stumbles upon the scene and rescues Ada who is pinned down and unarmed. Annette then flees and Ada follows.
Later on in the game Claire and Leon will encounter Annette in the underground research facility. Annette is informed that Sherry is no longer in the police department but in the sewers. Annette tells the duo that William is after her. Annette then makes her way to the underground labs where she has one final encounter with her husband. In his third stage of mutation, Annette is able to see remnants of William's face on the chest of the monster in front of her. Annette raises her gun to shoot William as he charges at her with his clawed hand. Leon and Claire discovers her body as a pool of blood emerges from under her. With her life coming to an end she gives the duo the location of the antidote to cure Sherry, and a final message to her daughter stating that even though she has failed her as a mother, she always loved her.
(Key note guys, this scenario is presented in the Resident Evil: The Darkside Chronicles game. In Resident Evil 2, this can happen or Annette can die after suffering injuries due to the facility coming down on her.)
Non-Cannon Scenario (Events which doesn't fall on the overall plot of the series)
In the Leon A/Claire B Scenario things are fairly similar until Annette corners Leon in a corridor and informs him of the true purpose in Raccoon City. Leon doesn't believe her and Annette is about to pull the trigger when the ceiling falls on her. Leon leaves her and as he heads to the breaker Ada arrives and pulls her gun out on him and orders him to give her the G-Virus. Leon refuses to give up the G-Virus. Not wanting to shoot Leon she puts her gun down but in turn is shoot by Annette Birkin who dies from internal trauma.
In the Claire B part of the story, Claire runs into Annette in the sewers where she saves her from the mutant alligator (if Leon didn't kill it the first time around). After Sherry is cured she talks to her mother who apologizes for ignoring her but lets her know she has always loved her. Annette then dies in her daughter's arms.