Originally Posted by Butterfli19

I haven't read the 10 pages of comments to this so as a single mother of two kids now 23 and 18, I will offer this:

You know your daughter and her friends. Contrary to those of you who think you know otherwise when a group of kids get together it isn't necessarily to have an orgy. Most kids are smart and careful. She's 17, not 12. She will be on her own soon and needs to make her own decisions. She obviously trusts you and respects you enough to tell the complete story.

I say let her go. You can tell her how you feel and how you will be concerned but the decision is hers. Let her know you trust her and she will do the right thing whether you are involved or not.
***
An aside: Being a parent isn't about controlling your children or teens with "my house, my rules" or "my way or the highway," or comparing your teen years with theirs. It's about treating them with respect and supporting them, not judging them. This is their life, not yours.