I don't have any advice on how to frame the upcoming conversations, but I am wondering since I recall she has undergone a lot of changes (in her life, and also just recently) - if I recall, she is the one who was grade skipped to her sister's grade... if so, maybe you need to sit down and talk to her about whether your DD is finding that she thinks she needs to be able to "think faster" or such. And also, when there is no immediate problem to be solved - maybe it is an idea to talk about how you can help her when these intense emotions of "must get this done right now!" - see if she can think of strategies you can implement or you make some suggestions that helps.
Also - something that I have thought about whether I would explore when my kids are older is something like a shared journal or book where you both can write your perspectives in the same book, and write down the feelings, concerns etc. Dealing with intense emotions when they burst out is not usually the right time for this, but most likely if it explodes like that, it is buried in calm times, but reachable in ways maybe she can write it down. I am a big journal writer myself and during some of the major emotional turmoils I was struggling through, I wrote volumes (literally).
