what movie is this? (vampire)?

It was a vampire movie.
About this guy who goes into this place with all these seductive women
that are seducing men, and then killing them. He ended up escaping,
but was bit.
He went to his ex girlfriend for help(she writes vampire novels) and
in the end she helps him kill the vampire who bit him, and becomes a
vampire herself (she was just using him so she could become one) and
he ends up in a mental institution.. Or prison... Or something can't
remember.
but yeah then she goes into the cell at the end and drags him under
the bed or something like that, and you cannot see her on the security
cameras
Sorry my description sucks