Psychotic villainess Bethany
Bethany (Lexi Ainsworth) is the secondary villainess from Obsession: Her Final Vengeance, the third and final film from Lifetime's Obsession Thrillogy (airdate July 12, 2020).
Bethany is a patient at a mental hospital; having been committed after she attacked her sister, Charlotte, with a knife due to her belief that Charlotte was trying to steal her boyfriend. She was under the supposed care of newly hired nurse Courtney, who was actually Lisa Bransworth, the sister of Nicholas Bransworth (aka Blake Collins; the overarching villain of the first two films). Lisa bonded with Bethany after telling her about main protagonist Madison Turner, who Blake was dating before she killed him in the second film.
In actuality, Blake/Nick was a psychopath who got close to Madison to rob her sister Evie, and she killed Blake in self-defense after he kidnapped her. As part of Lisa's heel turn and vengeful vendetta, she omitted those details and painted Madison as an evil person who killed her innocent brother, manipulating Bethany by telling her that Madison was just like Charlotte. Bethany voiced her fantasy of killing Madison, leading to Lisa enlisting the deranged psychopath to do so after Madison ended up committed due to Lisa's sabotage.
The climax saw Bethany receiving a knife from Lisa to commit the murder, and afterwards, the evil Bethany entered Madison's room with the knife and lashed out at her for hurting "Courtney." She ignored Madison's protests that Lisa was a villainous psychopath and continued lashing out at Madison before lunging at her, after which Madison fought off Lisa's enlisted assassin. Lisa ended up killed by Madison's boyfriend Wesley after a scuffle, and as for Bethany, she was (most likely) returned to her room and faced charges of attempted murder.