I'm not a mom, but it wasn't so long ago that I was the 17 year old girl wanting to do something her mom didn't approve of (I would have never thought of sleeping over with a boy though, lol).
When I was that age I had my fair share of arguments with my parents. They didn't want me hanging out with so-and-so, or going to such-and-such a place/party. Did it make me mad at the time? Heck yes.
But now, at age 21, I look back and laugh at myself. I see the wisdom in their decisions and honestly rue the way I treated them. Hopefully your daughter will be able to look back in a few years and feel the same way - and she, like I, will feel thankful that you were strong enough to say no.
My only advice is do it in a gentle way. Try not to get angry with her. A gentle, but firm response, in my admittedly inexperienced opinion, is the best way. Best of luck to you,...I'm dreading the day I get 'paid back' for all the crap I put my parents through!!