I know what I did to Mr. McTerny was unforgivable, and I wish to God I could undo it, but you have to understand. What Billy and I have is special; it's real. I'm not some pervert. I love him, and he loves me. Is that wrong?
~ Ms. Austin defending her illicit relationship
Ms. Austin is the main villainess from "Something's Rotten in Redmund," episode 4.20 of The Mentalist.

She was played by Emily Bergl, who played Rachel Lang.

Ms. Austin (age 35) is a drama teacher at Redmund High School, and in the episode, she was leading the class in a performance of Hamlet. During one of her classes, Ms. Austin noticed one of her students, 16-year-old Billy, and asked him to audition for the play. The pair eventually engaged in a sexual relationship, hooking up after rehearsals. Late one night, English teacher Jack McTerny caught Ms. Austin making out with Billy while he was jogging outside, and he threatened to inform Principal Snyder about what he had witnessed, while stating to Ms. Austin that she'll go to jail. The villainess sent Billy to stop McTerny with the claim that she only wanted to talk to him. Billy followed McTerny to the batting cages and confronted him, but at that very moment, the evil Ms. Austin grabbed an aluminum bat and struck McTerny on his head, killing him instantly.

Patrick Jane had figured everything out by the episode's climax, but to make his reveal, he first had to get Jeremiah (a cast member in the play) to pass out. Jane was enlisted to replace him, and it was there that he revealed Ms. Austin and Billy's illicit relationship and roles in McTerny's murder. The villainous teacher attempted to escape after Billy fingered her as the actual killer, but she was stopped and handcuffed by Lisbon. At CBI, Ms. Austin confessed to the murder and stated that killing him was unforgivable, but she defended her relationship with Billy, claiming that they were in love. Other than McTerny's murder, Ms. Austin was also arrested for statutory rape.