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.
Yes, DD was accelerated into her big sister's grade. It has gone so smoothly - thank you for pointing out that she might yet be dealing with the change. Also - just tonight we were discussing starting another journal. I told her I would read my 6th grade journal to her and her sister so we could compare 6th grade experiences. I have kept diaries/journals my whole life.
