I'd just like to add that please have your PT check each and every one of here neck & posterior shoulder muscles in (relatively) isolated positions. They have protocols for neck muscles, shoulder muscles, rotator cuff etc.

Heres a hypothesis, a long time back when sleeping in a certain awkward position, a muscle is "switched off" - the brain perceives it as being under threat of damage, or its contraction causing damage. Others (which are not designed for the purpose) compensate. The pain goes and comes as long as aggravating activities are kept to a minimum.

Injured folks automatically - without realizing - tend to do that. Over time, the repeated trauma on the overactive muscles or their impingement on additional nerves etc - flares up the pain & the brain, nervous system say enough.

Reason I state all this is because this is the case for many & since you are in the US, trust me, good PTs are many.

You may have to travel to find them but the effort will be worth it, also some answers can be real simple. Reason I am hoping that the answer is straightforward, is because fingers crossed, your daughters "complex results" have come back ok. It could well be something this "dumb" which is causing so much discomfort. Good thing is she can recover fast!