Could it be CFS? She's coming up on the 6 month mark, and according to the diagnostic criteria for CFS (I'm going from criteria from about 20 years ago, I knew the researchers who helped develop the CDC criteria then) you have to have had the symptoms for at least 6 months, and other possible causes need to be excluded. However, depression is specifically listed as not excluding a CFS diagnosis. The Aussie researcher who did a lot of work on this (I saw him present a paper on it in 1988) is Prof Ian Hickie, a psychiatrist. He proved statistically that depression in CFS has the same incidence as depression in the otherwise healthy population - 25%. He also made the point, often, that if you HAVE the symptoms of CFS, you would be pretty strange to NOT feel depressed! I concur...
It is possible that doctors have been thinking CFS, but with symptom onset less than six months, they could not really go there before now.
Sleep study will be useful, whatever the problem. Blood tests can rule out other more serious conditions but I'm betting that the findings of blood tests and sleep study will both be inconclusive (very frustrating). In which case - that is the time to ask if CFS should be on the table.
To live with CFS - it is natural when you feel ill or exhausted, to go to bed and rest. And it is natural when we care for someone like this, that we allow them to do it. But with CFS you have to make the mental transition from short-term acute illness to long-term chronic, and change mindset towards the condition. That doesn't mean you totally ignore the problems and pretend nothing is wrong (which is how some doctors have handled it - badly, in my opinion) but you do need to learn what you can push through, and what you can't. Rest when you need to but limit it somewhat. Push a little but learn your limits. Do as much as you can while you can then rest little and often.
If it's CFS, then even her waking moments will have "brain fog" affecting her ability to learn. Again, you would find the same with slow recovery from Epstein-Barr (glandular fever). I lost a year of uni to glandular fever; I had recovered physically, or so I thought, after a couple of months. But when I looked back at photos of myself a year later, you could see the puffy face, the exhaustion etc. I remember an exercise at uni in statistics which randomly put us into three groups to exercise. One group had to stay in the lab, the next group had to walk up two flights of stairs and back, the third group (mine) had to do four flights of stairs. We then had to measure our pulse rate (having already takern resting pulse) and the results entered. My results were so badly out of whack that the lecturer made me lie down on the floor to rest until my pulse rate slowed below 130. My data set was removed from the class data because you coud see on the graph, it was one wildly aberrant result. My glandular fever history (a year earlier) was considered to be the problem.
I did not get CFS from that episode of glandular fever. I recovered from the glandular fever, but it took about 18 months.
Marg