Teens and Their Moods

At what point do you start worrying about your teen daughter's boyfriend status? My daughter has liked the same boy now for nearly a year and they seem to get along wonderfully, but as of late, he has been going through some really tough times at home with his family and when he gets upset, he passes this upset mood onto my daughter, which in turn passes it on to me. I have explained to her that when he gets mad and doesn't want to speak to her, then she needs to just leave him alone....no phone calls and no texts, just total zip. Eventually, he calls her with the " I'm sorry" stuff and then she's smiling again. I told her that life is too short to be worried all the time, heck, there's all her other friends to call and chat to when he's all mad.