And as for the person who thinks you were disrespectful for commenting that you felt YOUR DAUGHTER was showing too much skin....WT???? I think you had every right to ask your daughter to dress more appropriately. She is your child and unless she's an adult, you are well within your rights, and in my opinion - your duties, as a mother to request that your child button up.
I do think it might be a good idea to have a conversation with her later, just the two of you, about how he treats her and about having respect for herself.
I don't think the previous poster had a problem with the mom saying anything - but that she would say it in front of the boyfriend. And that was disrespectful.
It goes with treating others (including your kids) the way you want to be treated. If I had a wardrobe issue (button too low, zipper down, TP stuck to my shoe or whatever) I'd be embarrassed if it was announced loudly in front of everyone and would prefer it being mentioned quietly.