I'm really sorry for everything you have gone through as a family.
We had similar health issues and severe anxiety. We did the advise from school and that others have posted here of forcing child in everyday (against my better instinct).
We kept being told that in a short time child would be fine and problems would resolve.
I often would have to physically dress child (It was physically and emotionally draining for me as an adult) child as stiff as a board this wasn't an easy task. Carry child to car.
Child hyperventilating on journey and as white as a sheet.
Child forced into school by all sorts of tactics by schools. Child lied to by being told mummy hasn't answered phone.
School telling me that child was fine once I left but with no idea of just how much they were struggling.
Child self harming, child violence towards parents. Child not sleeping.
We asked for help so many times.
I watched my child who had already been through so much medical treatment become a shell. Time and force of school actually didn't resolve the issue but caused long term mental health damage
I will never forgive myself for ignoring my own judgement and listening to the school and society who kept telling me that child had to be in school. We will never undo the damage caused by school.
We did move to home educating when things deteriorated further. We should have done this much earlier. We have been judged negatively by the school and people in society really have no idea of what families like mine go through.
schools said child needs to be in school for their future but they need to understand some children would rather kill themselves than be made to go to school.
I don't know exactly what is right for your child @Palmtreesinthewinds but taking time to have fun together, to allow your child time to recover from her health problems, to remember what life is all about could reset the balance.
She is 6 years old if you defer school start till sept she will finish education 1 year later than her peers. What is 1 year in a lifetime. This maybe enough to reduce the level of anxiety.
Or maybe it won't and home ed maybe something to consider
The current set up isn't working (she isn't settling to school currently - my guess is that the school must be concerned to contact you to collect) and something needs to change