Child anxiety looks like anger

Hello, I'm looking for support and advice if please.

My 12 year old is really struggling.  We have had medical appointments and tests and they can't tolerate them or the social interaction. This results in them getting stressed and they are unable to speak or go ahead with tests. The more people try to help, the more stressed they become which has then led to them lifting their hand to myself and others.  When calmer, they tell me they needed more time, and don't like it when more people get involved and the staff swap over or someone else comes in the room and they are all just waiting and watching.  An example was needing an xray and they just froze. They did try so hard, inching towards the machine but then this was interupted by someone coming in and then again by someone saying something to her and it made her retreat again.  This is also what is happening at school and she is struggling there too.

When this has happened, my child comes home then has the urge to bounce and jump about to destress and let it all out.  Unfortunately not everyone understands the need for this but I do.