"The Brave One" Erica Bain "you become someone else"

"The Brave One" is on my list of great movies as others with Jodie Foster.
Her caracther Erica Bain suffers a violent aggression and with detective Mercer, Terrence Howard, the movie raises numerous questions.
I'll leave this quote to summarize what Erica has been through:

Detective Mercer: How did you... pull it back together after what happened to you?

Erica: You don't

Detective Mercer: I'm sorry.

Erica: No, no.

Detective Mercer: Jacked-up question, man.

Erica: It's a fair question. You... you become someone else. A stranger.