Omg she's only 13... what do I do?!?

Ok, well, I have this friend who's 13, and she's in eighth grade (I'm a sopre, and 15.) and she has a boyfriend (he's 14, and stayed back). They started dating back in the spring, but she was 12 (they started dating like, 4 days before she turned 13). Well, first, she told me that they make out in a clroom everyday after school before they go to practice with their teams for sports. Then, once, she was (rudely) IMing him when I was at her house (and ignoring me) and I saw him saying something about "I was about to unon your shirt and the teacher came in." and I was sitting there thinking "Oh My God, she's only 13."I mean, I'm 2 years older and I wouldn't do that... And then a couple days ago, she told me that she's given him a (in a very braggy tone.) I'm like, "Oh my God, what's next, ?" and she's a Christian... her family is all Christian and I'm pretty sure they don't agree with before marriage. I've known her FOREVER and I never thought she'd be like this... I just don't want to end up with a 13 year old, pregnant friend... what should I do? I know it's not my business, but it's really bothering me... I mean, she's only 13, and she's given him a ... she's not even in high school yet! I don't know what to do? And I try to tell her this, she'll laugh at me and think I'm like a "mom" or something, and boring, or something... you know? I just don't know what to do!