Best friend had unprotected sex at age 15?!?

My best friend told me a week ago that she had unprotected sex with an 18 y/o who is her boyfriend. I m really worried because she s been making the wrong choices lately (hanging out with druggies, having sex, sometimes even buying drugs for her boyfriend) I don t know what to do anymore. If I say something against what she s doing she ll get defensive and say that it s her life not mine. She says she s having cramps and having nausea. What should I do? What should I say? I told I ll be there for her no matter what but the way she s taking this is worrying me. She seems too relaxed about it, she told she doesn t care if she has a baby because it will be easy to take care of but I don t think that s the case here. Her boyfriend hasn t said anything about it either and I feel like he ll leave her when he finds out that she could be pregnant (he has a reputation for this). Please help me here!