My best friend is planning to get married in 3 months?

i want to tell her to stop because she's fallen in love with a VERY bad person, but that's very rude to say to her. i keep congratulating her, but even in the presence of family, the man will strike her, and she will just get right back up and pretend nothing ever happened. my sister tried telling her once, but the woman just yelled at her. I feel bad because she's a sweet girl, and very smart... She's getting married at 18 because she wants to have sex, and she was raised to never have premarital sex. is there a way i can make her snap out of this? The man keep threatening her, and myself. he's been arrested multiple times, but his mother bails him out, and i just don't want my best friend to go into that. Please please help me!