Friend jealous of girls around her boyfriend...

Ok so shes in 7th and hes in 8th. They have been dating for about 3 months now and she always gets jealous of other girls around her boyfriend. Like if he sits around girls at lunch, intervention, or on the bus. This girl (Abby) likes my friends boyfriend and sits with him on the bus even though he claims he doesn’t like her.) A friend of hers that rides her boyfriends bus always text (cassie, i.e my friend) and tells her. She gets pissed and I have to listen to her go on and on. I use to only half listen until she brought up my boy friend. She asked me if I would be pissed if he hugged other girls right in from of me. I said I would be, if it didn’t look like a “friendly” hug. She told me that’s what her boyfriend does. I suggested she break up with him because I dought hes worth it and she won’t see him much next year. She considers it. But what I hate is they fight all the time and of course she gets her friends to spy on him and stuff. Then later that day their back together. Really they haven’t gone out for 3 months but they think of it that way. What can I do? I hate listen to her drown on and on. Shes clingy and gets jealous really easy. What should I say to her? I don’t want to be mean because shes my friend but sometimes I just want to slap her, and say move on. Thanks.