K.K.
You're doing the right thing. Everything you read says that kids need the routine, need early bed times. Keep up the great work!
And, I too, have been to "Love and Logic" - they set boundries - just like the other responder said.
I thikn you mean, when she's at a friends house and not spending the night, she wants to stay late. If that is what you mean, I think I would try talking to her about it ahead of time. Let her know she can stay til X time, but then it's time to go and it's not fair that she give you a hard time about it. :-)
Good luck, it's usually harder to do the right thing then to do what everyone else is doing! K.