Becky Wade was introduced as a student in an ethics class taught by main protagonist Kate Fischer, a former reporter. In actuality, Becky was actually Sandra Rose, the sister of Laura Rose--one of the victims of Max Hersog, the notorious September Slayer. Hersog was interviewed by Kate some time before the events of the film, with the interview featuring a confession from Hersog, which Kate didn't take seriously due to having heard numerous fake confessions to the killings beforehand. Kate would learn that Hersog was factual in his confession, as he killed Laura after the interview.
Sandra blamed Kate for her sister's murder, and she exacted vengeance towards Kate, recruiting Laura's fiancee, Anthony, in her plan. The plan involved the villainous pair enrolling in Kate's class, with Sandra going by Becky Wade and Anthony going by Collin McTavish, after which they would stalk and harass Kate with reminders about Hersog. Their reveal began when Anthony (who shot and killed a student in the film's opening) appeared in his police officer disguise and held Kate at gunpoint, after which he took Kate to her basement, where Becky appeared and officially revealed herself as Sandra Rose as she tied Kate to a chair.
In addition to revealing her true identity, Sandra/Becky chided Kate for not recognizing Collin/Anthony, and revealed their true plan to not only kill Kate, but videotape the death and release it on the internet. After Kate's young son, Robbie Benedict, was heard in the house, Anthony captured Robbie and took him to the basement, where Sandra blindfolded Robbie before continuing their plan to kill his mother. At that moment, police--led by detectives Lucas Kelley and Melanie Sinclair--surrounded the house, after which Lucas phoned Sandra regarding Kate's well being. The lights being turned on allowed Robbie to escape, with Anthony chasing after Robbie and getting shot and killed by police when Anthony pointed his gun.
All the while, the evil Sandra threatened Kate; informing her that she would kill her if anything happened to Anthony. The vengeful villainess saw the photos of Laura in Kate's possession, with Kate stating that she was trying to know Laura, only for Sandra to snarl that she would never get to know her--while holding Kate at gunpoint. After hearing Lucas enter the house, Sandra waited in ambush before striking him with a two-by-four, only for Kate to later knock out the villainess and escape. Afterwards, Sandra/Becky was arrested (off-screen) for her attempt to kill Kate.