These drs specialize in alleviating head pain, for whatever reason, i.e. migraine, tmj, trigeminal neuralgia
, etc. You did not say where you live but I know in the US that there are only a few and the wait list can be months.
She needs to drink as much water as she can as dehydration can also be a factor, especially if she is not eating well. This can cause blood pressure drops, especially on standing.
There is a neuro that checks this site pretty regularly.