the five 'teen' girls represents different personalities; innocence, strength, rebellious/devil may care attitude, fear/stupidity. loyalty/naivete or you could say split/multiple personalities. Yes, Baby doll is a sexually molested crazy teen girl that is the 'new recruit' to the asylum/brothel(I got the impression that Blue and the other orderlies were also sexually abusing/seling the girl patients way before Baby doll's arrival).
Og bisan nabuang sya, she still wanted to escape from the asylum(which is the game quest mode). I think it was her way of coping with her dark reality, escaping into her mind, making her escape to freedom a fun (her way of fun that is) ride where she's in control and has awesome battle gear to combat the abusers. In reality, she could have gone berserk/starting riots/fire/stealing things/etc. but in her crazy teenage mind, it was she as a gung-ho warrior with her A-team fighting battles upon battles towards freedom.