I believe this should go two ways.

Yes, it is the doctor's medical license that backs him up ... but,

If she is too big on the "Doctor says so," someone might want to make the doctor aware of her attitude.

I used to work for a dermatologist ... and I was always suggesting things to the doctor and his 2 physician assistants. I increased his yearly income (in one year), from $360,000 to about $3,000,000.

Making more money should always be on the minds of everyone in the office (effectiveness and efficiency). If this lady is simply "doing what the doctor said," then she may be missing some extra income for the doctor ... if she were simply putting a bit more thought into it.

Everyone in the office should work as a team (her included) ...