My son had anxiety and meltdowns at school (and at home) that were very similar to what you describe. He'd become overwhelmed by either anxiety, sadness, frustration or anger and then lose it. The social worker helped him create a 5-point scale that he could use to monitor how he felt. It was something like this:
1- I feel really good right now
2- I'm a little worried/tense but can handle it for now (take deep breaths)
3- I'm starting to get upset and should tell someone
4- I'm so upset I need some help
5- This is bad. I need help now!
The scale was set up with his input, so the words were his (I paraphrased, don't have the scale in front of me right now). He paired the words with icons for each number that had a different color (one was green, 5 was red, etc). Then he had a "full version" of the scale in his desk and a 3x5 card version with just the icons on it taped to the top of his desk. She also made him a small, laminated version to carry in his backpack or pocket.
This worked really well for him at school, most of the time. He used this during 1st, 2nd and 3rd grade. There were still times he lost it. And, unfortunately, the kids learned how to push his buttons and get the full blown reaction from him. And, also unfortunately, the 2nd grade teacher was not very supportive in general. But the 3rd grade teacher really tried to help him use this scale. You need to have someone on board in the classroom to help out, so your daughter has someone to go to for help with calming down - whether that means leaving the room, finding a quiet corner, or whatever.
Hope that helps. best wishes for finding something that does help. I know how hard it can be!
