BF IS POSSESSIVE!!

Okay, imma edit this post ... technically it's not me it's my friend but she doesn't really want to download the app so I posted for her. I did really give enough details before but there are stuff she doesn't want to be known so I'll give more details... but not too much. Basically, she's just turned 19 last month.. she's been with this guy for about 2 years and it's her first relationship. She moved out of her parents house and he moved out of his parents house and they built this life together. So she feels like if she leaves she she needs to start all over again. She can't move back into her parents house because it was a bad environment. She's tried since April last year (when he started being possessive) to break up with him, but all the time she tried it would end in a fight and he makes her feel guilty. She met that other guy around the same time as her current bf, but she stopped and kept him away because she had a bf but lately since her relationship hasn't been the best (her and her boyfriend are always fighting, her bf won't let any guy talk to her or vise versa) this guy is really sweet and there's not really anyone she would move into a place with because she's scared and doesn't want to. Her bf said that even if she cheats on him, he won't let her leave and she feels trapped but doesn't know how to leave. I've convinced her to ask the nice guy if she could move in but she still needs to break up w her current bf but doesn't know how... I've never broken up w someone so i didn't know how to help..