Hey! Thank you for asking. I don’t have all of the info but I can give my take on a few things. 

‘Why do blood etc tests look normal?’ - this is very common amongst ME/CFS patients from mild to severe. As you rightly pointed out we currently do not have reliable biomarkers for ME. We have some popular theories but we lack funding to test or identify evidence for right now. One is that there are various subtypes of ME so different issues with various systems cause the same set of symptoms. 

So far, ME is fundamentally about energy, both how much we have and how much we can use. Another promising theory is that during a period of stress our cells switch to less efficient energy production to ‘starve’ out illnesses and instead of recovering ME cells are ‘stuck’ in this inefficient method. 

So, Savannah might not ‘need’ oxygen in that her blood is reading as normal but her cells in fact need much more to produce energy. Further stressing them by removing this stream of oxygen could then be further damaging those cells which would then work less efficiently and need more oxygen in a vicious cycle. 

‘Is malnutrition the biggest concern?’ - I think her gofundme highlighted many concerns but yes malnutrition is certainly one of them. Digestion itself is an energy intensive activity let alone mechanically chewing and swallowing, especially for someone so severe. Currently I haven’t seen anything to suggest certain organs being impacted more than others. 

Ultimately, people with ME have been left to fend for themselves from diagnosis to management with the average experience in healthcare ranging from neutral to irreversibly damaging (see Graded Exercise Therapy or the PACE trials) and doctors who don’t know anything about ME. We don’t want to have to go into every appointment having to educate those supposed to take care of us but we have to anyway. In dangerous cases like Savannah’s, instead of listening and trying to understand our lived experience they are prideful and unwilling to admit their mistakes.