My DS is similar. He is just about to turn 6 and we finally seem to be coming out of this.
He used to have over reactions over the slightest things, even me just asking him to do something basic like put his shoes on could cause 10 mins of hysterical sobbing.
It is exhausting; so I completely understand you feeling frustrated about it.
I was starting to wonder if he had some undiagnosed SEN as it was getting so difficult, but at school he never behaves like this, and his teachers have never raised concerns.
We basically tackled it by not feeding into the drama. We created a cosy corner in his playroom, that was his safe space and I encouraged him to go there for quiet time if he was getting overwhelmed.
We try to do as much positive reinforcement as we can. He's very hard on himself if he makes a mistake so we try to point out all the positives as much as possible.
We signed him up to a martial art class to build resilience and confidence. It took weeks for him to get into it but now he really loves going.
Sadly though, I think most of it is just a phase and you have to do your best to keep your cool as much as humanly possible. If you need to walk away from her, go to another room to calm down. Do what you need to do.
Like I said my DS is almost 6 and I have noticed a massive improvement. Good luck.