What the member has asked is, essentially, in reference to secondary illnesses. It is a very good question, and it does come up.
I also want to advise the member that this comes up for physical injuries too. One of the things that happens to amputees is that they lose a lot of surface area of their body, so their body tends to overheat. There have been cases of amputees receiving care for their original condition, but then having to go back to the hospital because their body constantly overheats. When they turn to VAC for service for that, they wind up having to jump through a lot of hoops to prove that it is part of the original illness.
Grinding your teeth at night is part of what happens when you are having nightmares and night tremors, so yes, it is also part of post-traumatic stress disorder.
The lady's question is a very sound and accurate one. We all run into trouble trying to get secondary care for previously approved primary care conditions.