I second what Jelly has said. I've kept mine back on advice of our GP until proper support was in place for her. Our situation was a bit different in that she was physically very ill too & missed 2 years of secondary school as a result of that. She suffered badly with SPD, anxiety etc on returning to school, so needed measures in place fir the same support as your DD needs.
Don't mention home schooling. If your DD becomes to I'll fir school, it's still the schools responsibility to educate her whilst she is registered with them. This includes providing EOTAS tutors in core subjects for up to 5 hours a week. We were luck in that it was offered without my even knowing about it, but I've seen a lot of talk on forums where this isn't he case. Schools avoid it as it costs them, so they may need a push.
DD had a toilet/breather pass that allowed her to flash it & leave class without an explanation if she felt overwhelmed, sick, bad stomach etc. She didn't really use this as she felt embarrassed standing up in class, but knowing she had it did help stop her mind going into over drive with worries of passing out, accidents etc. So it helped calm her, even though she rarely used it.
She had access to a nurture room, which again she didn't like to be seen to go to, so she was allowed to spend lunches in the library.
She moved class in one instance as she was stressed by the teaching style.
She had access to counselling, but again found her own way by befriending the toilet attendant. DDs school had cleverly placed a trained counsellor in the toilets where the kids would run too if overwhelmed. She was an absolute godsend to DD on bad days.
Discuss homework targets etc. This was an area of major stress for my DD to the point of frequent hysterical meltdowns, that left her exhausted & ill. I found that a copy of the marking list, which was a clear breakdown of what she had to do/include in her work to achieve the various grades allowed her more control. She found writing tge piece she wanted, then going back & padding it out with the points she missed gave a structure fir her to work to that helped her feel less stressed.
Seat at front of class & with a quieter group. Moved into quieter classes if possible.
Lunch pass that allows her to miss the queues & noise at lunchtime.
In some cases allowed to leave class a few minutes early to miss the crowds in the corridors changing class.
Would she benefit from a fiddle toy?? These help mine to focus. She now has rings that are fiddle toys so again not obvious
Does school have any yoga classes?? This can help her control things a lot, especially the breathing techniques. Which helps their confidence.
SENCO support - sit with them & your DD to work out a plan fir her
How does her school uniform feel to her?? Mine really struggled with rough, or stiff fabrics & it was a big distraction to her, so confessions here could help too.
Get your GP on side to support any requests & referrals to CAHMs for assessment etc
Push for assessment for extra exam time, rest breaks, quiet room. They'll likely refuse if she's doing well in class, but remind them that you thought it was about allowing DS to reach "their full potential" not just about meeting school targets. Use examples of any G&T etc when she was younger. This got my DD assessed after initially being turned down, even though it was teachers who suggested applying🙄 & they apologised for not realising just how much she struggled with processing, panic attacks etc in exams & class. She still needed anxiety medication to get her through GCSEs, but after years of feeling frustrated & unhappy with her results as she knew she could do more. She was very happy with her GCSE results
Do you have a local Wellbeing Metal Health Service? You can self refer your DD there & she can be assessed & access counselling that way too.
I wouldn't worry too much about the lack of friendships just yet, unless your DD is unhappy about it of course. Mine was overwhelmed in school & so actually couldn't cope with the additional stress of friendships. When she had better support & felt calmer in school, that all came naturally & she's ended up with a small group of close friends who are all more alternative like she is.
Mines much calmer in college though. I've now realised just how stressed she was with sticking to school rules & dress codes, especially ones she didn't agree with.
Good luck