Help plz!!!!!!!!!!!!?

one of my best friends, were gonna say his name is tom, likes this girl, umm... ally, and me and tom are really good friends, but thats it, we dont like each other as more. and tom is a really good person, hes a christian and goes to church every sunday. but this girl he likes, ally, is.. well, let's say she's done just about everything in the book if u know what i mean, and she's only 15. she has a boyfriend, but she likes eric and about 10 other guys. tom REALLY likes this girl, and i've tried my best to talk him out of likin her, bcuz i support eric on whoever he likes.. but she'll hurt him, i know she will. and his mom wouldnt agree w/ him goin out w/ her, so he's gonna sneak behind her back. and i know i probably need to stay out of it bcuz it's his choice not mine, but i dont want him to get hurt. what should i do???? o and ally was the top person on the "most likely to be pregnant list" that went around school