I think what Lad might have been trying to say is that you aren't really setting boundaries. In the college example you gave, you did not say "It's 3 am; I have to go to class in the morning, and you all need to leave." You made a more passive comment suggesting that they leave without saying the words. I think what you might need to practice doing is voicing exactly what you want people to do, how you want to be treated, etc. Also, perhaps adding consequences to boundaries not followed through -- again, in regards to the college example, if they did not leave you could have called campus police or something (I don't understand how your college housing worked; every where I've been had RA's that enforced rules regardless of age).

I hope that was helpful without upsetting. I understand your feelings and I agree with you that I wouldn't let your daughter's friends take advantage of you, because honestly, not only are you being taken advantage of but you also enabling them to stay the way they are. Setting up firm boundaries helps both you and them. And one more side note... I think your daughter has very good intentions, but I think it would be better for her if she went in the field of social work instead of taking them in and trying to help them get better. She might be having the same weak boundary issues you are having and is enabling them to stay the same as well.

Again, hope I didn't upset you. Sending warm thoughts your way