Bay Smith is a main character. Once a guy, she was turned into a girl several years ago. She keeps this fact a secret, and only a handful of people know.
She's now a struggling actress whose roommate is actually her daughter from an alternate future timeline.
I think I can ID four of the posters:
Laura (Gene Tierney, Dana Andrews)
Invasion of the Body Snatchers
King Kong
Gilda (the signature film of Rita Hayworth, a.k.a Margarita Cansino)