@kmg218 Maybe I can offer some help. Has your daughter gone to a comprehensive medical center or a university hospital. These are usually a cut above community hospitals because the doctors like to do research and try new medications or treatments. You can just call and see if the doctors treat ED and POTS.
Another”thing” to try are these two organizations who try to help those with ADs. They are:

GARD. https://rarediseases.info.nih.gov/
NORD. https://rarediseases.org/

Both of these sites are well worth your time and they have lists of doctors for you. You can also go to the Autoimmune Association website and look for list of doctors. Good luck in the hunt—I’m sure you will be successful!