Please please people...
Telling her that getting up to take a walk will make her better is very old school. Yes there are many people for whom this will work. But not people with Chronic Fatigue Syndrome.
I have had it for almost 20 years. And before getting sick I was fit, in-shape, healthy and of a good weight. Then I came down with what I thought was flu....but it didn't go away. My GP told me she thought I had it. I was lucky to be in a city where there was a true specialist. After testing me for everything else, I was finally officially diagnosed with CFS and FMS (Fibromyalgia).
CFS is mostly diagnosed by exclusion, though you have to fall into the set of symptoms given by the CDC. You can go to their web site. Though there are better sites run by various advocacy and support sites.
Do more research and maybe you can find a Dr who specializes, or at least have information with which you can work together with your present Dr. If he/ she is amiable to helping you with your condition ..stay . If not , find a new Dr.
Good luck