I feel so bad for her. I think I would call my insurance provider and get a listing for everyone who takes your insurance and then call them. Find a doc who will do a complete workup on her.
I know a few kids who have had Mono and they were back to full schedules in a couple of months if they got plenty of rest and were careful about getting other illnesses, hand washing really does help...lol.
My granddaughter was in the hospital last July with Strep. The pediatrician tested her 3 different times for Mono. He was sure that was what it was. All 3 tests came back negative. They were done at both his office and through the hospital while she was in. Her right tonsil was pushing the left one out of it's way and her Uvula was completely hidden. She had 102+ temp for over a week and was on IV Rocefrin. She had to use Mr. Thirsty, the suction tube, just to get her saliva out of her mouth since she had no room to swallow. I thought she was going to die. I truly did.
She weighed about 56lbs when she went in and when she left she weighed 43lbs. She was on the show team at the gym, took regular tumbling, tap/ballet, and Hip Hop classes. She also did BMX and soccer. She also got a part in Cinderella in September.
She took time to rest. I let her go to bed as early as she wanted, she could sleep in on the days out of school as late as she wanted, sometimes it would be 10 or 11 before she woke up....
We dropped BMX and soccer and haven't gone back yet. She is doing all her classes at the gym since Cinderella finished in October.
The point is, if she had not gained her stamina and her weight back we would have been seeking other docs to find out what was going on. I think your daughter has something more going on and only a doc who is a diagnostician can fully appreciate all her symptoms and do the proper testing to find your answers.
Every field has at least one of those docs who are just gifted in getting to the bottom and finding the answer. I hope you find the one you need for your and your daughter's peace of mind...and body too.