self-esteem whore
A girl or woman who regularly goes out seeking anonymous sex not because they enjoy it, but because they feel that it will increase their self-esteem. However, it often has the opposite effect, though these poor, misguided girls often continue in the hope that they achieve the desired effect.
She went through the London bars each week looking for anonymous sex with any guy that would have her just to feel better about herself. She's a self-esteem whore.