Originally Posted by Mamagus
I have a 25 year old daughter ...
In my opinion: She asks this time and you give her a no? The next time she won't ask. She'll find a time and a place to rebel without you ever knowing anything about it.
It is all well and good to be the Mom who takes the high moral ground, but unless you plan to escort her everywhere she goes for the next 4 years, she will in all probability have sex with a boy before then. You can be pro-active and provide her with birth control or her own supply of condoms, but if she wants to, she is gonna do it with or without a sleepover party. It takes a few minutes!!
By all means call the parents and check out where the boys are sleeping... but unless you're going to supervise her, you have to give her "The Talk" and hope for the best.
Letting your child make decisions on their own about their life's path is not being amoral and uncaring. Not if you've already been the voice in her head guiding her decisions thus far. If you've raised her right she'll be fine.
My daughters are now 34, 31 & 26. I was the one that hosted the prom parties. Everyone slept on the living room floor (I didn't sleep : ) ) and I had to speak with each parent in person to make sure the kids weren't pulling a fast one! No drugs/alcohol on premises and everyone had a good time.
That said, you have to trust your own instincts!