A.W.
Explain to her why it is not appropriate for her to stay at their house. She is old enough to understand, she is becoming a teenager! Let her invite the girl over for a sleepover at your house instead.. Also, she probably needs more one on one time with you. It might be hard with a little one and will be more so once the third arrives, but make time ~ a mom and daughter date, take her to the movies, to the mall, to get ice cream.. something where it is just you and her. Try to do that at least once a month, every two weeks if you can manage the time. Tell her that you're sorry that she had to grow up so fast and that you only want what is best for her. Sometimes, just talking to her when you're not in the middle of a battle will help.
Best of luck to you! =)