My mum is diagnosed hEDS and my son was finally diagnosed last week, after being fobbed off for years. I have never bothered with an assessment for myself, but would almost definitely be diagnosed if I was. Other members of the family clearly have it, but remain undiagnosed. I have some complex issues, which almost definitely relate to it, but no-one in the UK/NHS ever manages to put together. Both my son and I also have dysautonomia/PoTS and he has gastro issues, as does my daughter - in her case Mast Cell related.
Have a read of the EDS GP Toolkit and direct your GP to it. A Rheumatology appointment is usually necessary for diagnosis, although the idea of the toolkit was for GPs to be able to diagnose - but they don’t. (Join the EDS Support UK and HMSA for up to date research and advice.)
Unfortunately not all Rheumatologists are created equal and there are a significant number who will tell you that hEDS does not exist. It is easier post 16, under adult care, as there is a massive problem in the UK with refusal to diagnose hEDS in paediatrics.
Re Physio, you need a high grade, EDS aware physio. Standard community physios are generally of little help and both my son and I have been bounced back to the GP by them, as they couldn’t help. If you get a Rheumatology referral, they usually have their own specialist Rheumy physios, who are much better.
A diagnosis will help with school/college/exam accommodations, although technically, you shouldn’t need a diagnosis, just support from a sympathetic medical professional and a decent SENCO.
Pain and fatigue are often the hardest to deal with. Learning to pace is vital. Also developing a personal toolkit for what works for pain. It will be different for everybody, but things like warmth (wheat bags, hot water bottles) ice packs (for injuries) relaxation, mindfulness and distraction are helpful. We find painkillers don’t work for us, so rarely use them. Putting together a ‘care box’ of things that help, that she can access whenever she needs them is handy. (Can be anything from the above list, plus things like cosy blankets, fluffy socks, favourite treats, films, box sets and books, hot chocolate sachets - anything you know makes her feel happier.) Rest is important, but it has to be balanced with movement, as maintaining muscle mass and strength around joints is really important. Deconditioning will make everything so much worse.
See if you can get her checked for B12 and Vit D deficiencies (lots of people with EDS have deficiencies in these and other things such as iron and folate) and make sure she is getting decent quality supplements for them (sublingual for B12). Also Magnesium, either in the form of bath soaks/salts or supplements will help with pain and sleep quality. We take chelated high quality magnesium supplements and it definitely helps.