to be honest i'm a little weary of any college student pursuing a highschooler. not like a hs senior and a college freshman obviously, but any age gap that would create a decent difference in experience and possibly as a result, an unhealthy power imbalance of sorts. yeah it's just 4 years but in those really fucking formative years, it's quite a leap from 16 to 20. i mean 8 partners compared to 1, and he's her first... frankly i'm on your side here but i'm biased. i was one of those stupid teenagers that was so head-over-heels that an older guy was into me, and it did end up abusive and completely unbalanced. same story with all my female friends who got attention from the "cool older dudes" who turned out to be just looking for easy targets to manipulate. i know there are exceptions but i think it's completely healthy to distrust this kind of thing, or at the very least safer. but more importantly you're her dad, not her friend. of course she's gonna disagree with you here, but you're looking out for a minor that doesn't have the life experience to see this shit on her own. that said, you can't ground her forever and sadly you can't always protect people from stupid fuckin' decisions. out of all the friends i've had that made the mistake of trusting the wrong guy, only one of those said guys ended up with any legal retribution, and even then she and him were writing letters to each other while he was in prison. so right now i'd worry about talking to her about safe sex and doing damage control while you can, while keeping it clear that you are not okay with this particular relationship, and why. it's pretty average for a 16-year-old to be sexually active, i'm just sorry it's this kind of situation. let go of the idea of trying to keep your daughter chaste, that's a losing battle every time. that can of worms has been opened. it's about her safety and happiness, any parent would want to be sure that their teenage daughter's relationship is a healthy one. in potentially unsafe situations like this it's your right to put your foot down as a parent, even if you get the silent treatment, but like i said, damage control. teenagers who want to go against their parents' wishes are very crafty, i've been there. teach her to make safe, smart choices, and who knows, maybe this guy will end up having good intentions and it won't be a total shit show. just remember to try and tell her why you set the boundaries that you do, so maybe she'll hear some of the honest worry and love over that teenage indignation.