T.M.
The only thing I can say is to remove yourself from the screaming. Give yourself a time out, so to speak. She is learning that if she screams, you come running. I know it's hard, because you feel guilty and feel like you need to "fix it"; but in this situation, you need to do the opposite. Believe me, I know it's really hard but if it takes you going outside and counting to ten while she calms herself down, then do it. Reward the stopping and not the screaming. It's a process. But, she will get the idea that NOT screaming gets her further with you then the screaming does.