Really sad, because it impacted almost everything she did. She was definitely not a hypochondriac and seemed really well mentally balanced.
“She told me that it almost destroyed her life, because before she was very athletic and driven to achieve. Afterwards, any driven activity would cause her to crash. She had to pace her life and avoid almost everything that made her happy.”
That is the perfect description of the kind of tragic person afflicted with ME/CFS...an “A-type” personality who gets labeled a malingerer by certain folks who seem to get their jollies by coming onto CFS threads to mock CFS sufferers because some wife or girlfriend or co-worker on disability seemed to them to be faking!
What your girlfriend was describing is has the technical name of “post-exertional malaise”...a stupidly inadequate name which really means “total incapacitation after a pathetically tiny bit of exercise”.