Unprotected Sex

Moe
So I have this friend and she and her boyfriend are sexually active. There was this one time when they had a pregnancy scare because they didn't use a condom and she was stressed for about a week. She came to me a couple of days ago and said they had sex without protection again and when I told her she was going to get pregnant she got mad at me. She says it's her life and she's not going to get pregnant. 
I don't want her to get pregnant because she's only 15 and I don't know how to bring it up without her yelling at me telling me it none of my business. 
Ps. She's not on bc.
Please help