I am sorry to see that your friend is going through this. Keep talking to her. She sounds like she needs the support and isn't getting much else where.

As for her (close friend) tell her that she is better than that. He is too imature and she needs a man with stability (not his mommy's hand)

Maybe even mention this place to her. There is alot of good people with experience and healthy advise.

"She kept saying she was born with a guilt complex, she really feels guilty for other people, wants to be nice, wants to keep everyone happy, ect."
She needs to be happy and healthy before she can make other people happy. If she has no respect/self worth peole will keep treating her like a "door mat".Also, she is not responcible for her brother. He is responcible for his own actions. She odviously learned that herself if she used to have a "drug lifestyle" The most she can do is give him emotional support when he needs it. If he is treating her like crap then maybe he isn't ready to deal with his own "ghosts" and just takes his frustrations out on her.

JUST KEEP BIENG HER FREIND AND SUPPORT HER. BE AN EMOTIONAL CRUTCH IF NEEDED.
AND KEEP TELLING HER THAT SHE IS WORTH IT AND MUCH BETTER THAN WHAT SHE IS ALLOWING HERSELF TO BE.