My son used to do that when he got frustrated with the person he was with. That was after he used to bite, hit, then we went to screaming, now it is telling people they suck. I feel it all comes from frustration with that person they are dealing with. Have something with her that clams her down that she can go to when she gets frustrated. Teach her a coping skill she can use that is more appropriate, getting upset with a friend shake it off, teach her to shake her hands like shaking water off of them, they visualize things, she will see in her mind the problem flying off of her hands if you describe it to her that way. Three shakes and the problem is gone. Like Dorothy clicking her heels with her ruby red slippers. Sounds silly but remember we are dealing with kids so we have to make it fun. I have had parents tell me that they have taught their kids to "blow away" their melt down and the kids actually exhale, to them they are literally blowing away their problem and it works, but it takes time and repatition. Remind her to use her words over and over again with her friends, role play a scenerio that you have seen happen. While you are doing this you be her and show her how she should have reacted. First scream in her face ( yes I am serious) then do it again with the proper reaction. I am sorry , some might not agree, but she needs to know how she is making others feel! Sometimes we don't realize what we are doing until it is done to us. Hope some of this helps. Oh yeah, while she is playing, she might need to take a break to calm down with something, you might have to redirect her until she figures out how to do it on her own.