Break up

 So I have this girlfriend and it's a long distance relationship. We've been friends since the sixth grade(Were in 10th grade now) I feel like we are moving to fast and that we should try again when we're older. The problem is that everytime I tell her that we need to talk she goes on about her depressions and how terrible she feels and I don't want to add on to that by breaking up with her. What should I do. (Also she's polagoums she has 2 boyfriends and another girlfriend)