Molly

Molly(Transgender) is usually used to describe a girl who has gotten surgery to change her body parts but remained a girl there for when you think you're getting in bed with a woman but then she takes our clothes off she has you running out the door because you had a giant dick.

Boy: You wanna go upstairs?
Girl: Maybe we should wait till you see whats downstairs.
Boy: I guess that's why her name was Molly!