My friend's boyfriend beats her and she likes it?

My friend has never really had an intimate relationship with someone. She's battled self injury and depression and such. Both her parents were drug addicts and she grew up with her aunt who was a paranoid schitzophrenic and didn't have any friends for years. I met her a few months after she left and like overnight, she just started going wild. She did go to therapy (where she ended up sleeping with her therapist). When she started dating her boyfriend, he seemed respectable and pretty nice (I know him through my friends and they say he's great). I saw some bruises on her the other day and asked about them and she told me about her boyfriend. But she doesn't want help or anything. She said she likes him hitting her. She said the other night when they went out, two guys from her job talked to her and he got jealous. When they got home, he hit her. She said they had afterwards but avoided saying yes or no when I asked if he forced her. She just said she liked that way. She says if she thought she as in danger, she'd leave him. But honestly, I don't want her with him but she's like delirious or something. I don't know. What should I do? I've tried talking to her boyfriend and he says their relationship is none of my business. Part of me thinks he's just a spoiled little rich brat who thinks he can get away with whatever he wants. Please help.