Thank you so much for all the input, I wrote a long reply this morning but it doesn't seem to have posted.
My youngest son has severe food allergies, so we are quite aware of these and I am pretty sure these aren't a factor for her.
We have EDS in the family and Chronic Fatigue/Me is often linked to this, so it does seem a likely possibility. The EDS does leave her exhausted at times but this is on another level entirely.
We are aware of the spoons theory through EDS and are pretty mindful of her reserves, to clarify this through a diary is an excellent idea, I have started noting the amount of sleep, her moods and energy peaks and lows, I will try to formalise this to see if there is anything it flags up.
Swatsup I will ask re her heart rate, that's interesting - Both mine and my husbands family have rare members with genetic disorders and unusual illnesses, so we are familiar with not fitting into what is statistically the most likely diagnosis.
Our youngest has severe and complex food allergies, our middle EDS and possibly CFS and our eldest has a disorder that affects only 33 others in the UK. All seemingly unrelated disorders.
Green Elephant, the GP has done a thorough screening of bloods and has put us on the CFS path - is there anything particular that I should be asking about do you think?
If it may be something else and we can cut out months or years of trial and error by suggesting a few other possibilities that would be beneficial. (We have been there and done that with our eldest!)
We live in Devon and have been referred to Bath. Its likely to be June before we get seen.
Thank you Smurfy for all your thoughts, we are definitely going to be doing all we can to help her pace and get through the days enjoying the bits that are most important to her.
Raveon your DD sounds very like mine. how old is she? Mine is very anxious about goingto school, but ok once there. She often asks if I can sit in class with her and some days I have had to bring her home and calm her down before trying again a bit later. Once she is there she enjoys all aspects, its just getting her there, but after school she is totally wiped out whereas a year or so ago she wouldn't sit still for more than 20 mins or so, even sitting for meals she was keen to get back to physical activity.
I will spend time looking through all the links and rereading your posts.
Thank you all so much.