You are doing an awesome job. I do think that maybe days like this should be excused because it really appears that there is a LOT more going on than just gfgness. If your docs won't do tests then get new docs. Don't settle for "the results were normal" on lab work or other testing. get copies of the actual levels. I had docs tell me for over a decade that my labs were fine. My vit D level was so low as to be almost nonexistent and all the calcium in the world won't help the bones with-o it. So my calcium levels are great but only because it is coming OUT of my bones. The endo says that if he had seen these reports a decade or more ago, we possible would not be in the situation where my body won't tolerate vit D at all (makes me vomit profusely, even special expensive shots of it do that and require regular medications to stop the nausea.
Also, lab work can be normal but still telling you something. This is going to sound strange and obsessive, but you NEED to make a graph and get copies of any/all lab tests she has EVER had done, going as far back as possible. Often the TREND in the levels tells a lot more than the level itself. My mom was diagnosis'd with lupus years ago. She finally started doing this and when she got a doctor to look at it the comment was (and I quote because it is memorable) "Holy SH&&) This going up and that going down means you have X" X is an autoimmune form of cirrhosis. My mom barely drinks. She spent YEARS on medications that made this stuff a lot worse, incl one that actually did give her lupus (side effect from the TNF medications like Enbrel and Humira). She now has the liver stuff on top of the others and NO ONE would EVER have known if she didn't graph her lab tests.
If something shows on labwork, low thyroid would be the best thing. That is cheap and super easy to fix. the medications are very cheap ($4 list) and do a great job. I also think the sleep study should be helpful. One thing other than apnea that can cause what she is having is hypoxia. The oxygen levels drop in your sleep for some people. It makes you exhausted.
Does she have aches and pains regularly? CFS may be the issue, but it also can be fibromyalgia. I was about her age when mine started. It is often kicked off by a virus and I had my second case of chicken pox just a few weeks before mine started. Has she been sick with any kind of virus? Also does she have chronic migraines or occasional ones? It sounds strange, but it is possible to have a low level migraine that just saps your energy. People don't think they are migraines, but they do have some of the symptoms (one side, light/sound/smell sensitive, etc...) and they are exhausting. What does she do to treat a migraine?
I know that giving a teen diet advice is often as helpful as trying to get a pig to fix dinner, but diet can be an issue. I have mentioned this diet before here. Check out the Zone diet by Dr. Barry Sears. It isn't all protein or all carb or no fat. It is a BALANCED way of eating - 40% carb, 30% protein, 30% fat. Eat six times a day, three snacks and three small meals. One thing that I esp like is that NOTHING is excluded. Half a snickers and 2 oz lean turkey is a snack. An egg mcmuffin is a bit high on the fat but still is okay. This isn't a crazy diet. It is a way of eating and it really makes a difference. I was working in a bank and the whole dept decided to do it together. We were ALL shocked. HUGELY. Our productivity went up, error rate went down, everyone was more cheerful and we drank less coffee because we were not so tired all the time. I got my mom to try it. With her disease the docs said that her liver would NOT repair itself. That was the progression of the disease. Mom still tried this because it was common sense and not an out there fad thing. She also worked to cut her stress levels and a year later had another liver biopsy. The doctor was really shocked, triple checked because he thought that they mixed up her biopsy and someone else's and it would have to be redone. Why? Her liver GOT BETTER. They had gone into an area they had biopsied a few yrs bfore and had seen significant damage. It wasn't there. they did more tests and were shocked and asked what she had done??????? The ONLY real changes were lower stress and this eating plan.
I know I sound like some television diet ad, but this isn't about that. Food is our fuel. the right things help us and the wrong fuels don't. Balancing the carb/protein/fat gives you more energy in a week or two. You do NOT go "all protein" for a week and ignore the fat. You do NOT eliminate desserts. You learn portion size (compare recommended portion to regular objects like a deck of cards, ping pong ball, etc... this makes it a TON easier to keep portions under control and is a lot less PITA than measuring cups, esp in public) and it just works. You can even buy balance and zone brand nutrition bars for a fast boost. those brands have that balance and most others are hugely high in carbs or are just protein.
It may be tough to get her to see this as reasonable, but if you can find a way to make her favorite foods fit this (add protein powder if needed), it really might help the exhaustion. There are a LOT of Zone diet books out there so get a used copy and look at the recipes. they even have at least one cookbook.
What types of friends/support system does she have outside of family? She is a couple years younger than Jessie but being able to talk to someone who is going through a chronic health issue can be a HUGE help. Jess has a lot of problems and I am again frustrated at having no treatment for her that really works. I do know that even infrequent facebook contact with friends can give a big boost to her spirits. I would be willing to ask Jess to reach out if your daughter is able to use fb or email or even do chats. Jess is an odd child, mostly because she has an amazing amt of compassion and empathy. They may or may not click as friends, but I wouldn't have a problem.
I know your daughter can be manipulative. But right now, this does NOT look like that. Sometimes our kids are UNABLE to tell us what is wrong because it has been wrong for so long that they think everyone feels this way. Sensory issues and referred pain can also complicate this. referred pain is when one part is injured but you feel the pain somewhere else. Like when you eat something really cold and your head hurts instead of your mouth. Sensory issues just make the brain not able to sort the signals to let you know what is really going on. I often have my kids stop and concentrate on each body part, one at a time, to figure out what is really hurting. drives them bonkers, but it is the ONLY way to help them.
I know I wrote a book here, and I want to make one last suggestion. Write a Parent Report. The link in my signature will take you to the thread about it. It is an awesomely powerful tool and helps with doctors as much as with school. Sometimes they need the WHOLE picture with evidence of what has been tried to be put in front of them. Yes, a chart should do that but this make an impact and gives them info from other docs, etc....
I hope something I said helps. Take what works for you, ignore the rest. (((((hugs)))))