Do you work at a school with a Cheif Pilot?
I had a situation before, back last year with a student. I literally couldn't handle his attitude. It was just beyond me. One of those, real pretentious kinds.
Anyhow, I basically said hey, we are NOT getting along here(this was on the ground) and said this is it, I am getting you another instructor. One of my peeves is people who show up late... without a call, and then think they are entitled to everything. If someone shows up late, and I have 4 students scheduled with about 3 hours each, and someone makes it 45 minutes late to the first lesson, I am NOT pushing back the other 3. Not to mention, the airplanes were on a tight schedule.
At any rate, having a student that drives you nuts is not worth having. I don't care if it is income, I am willing to bet she is not your only student and there is most likely a greener instructor that will put up with her BS to get some time and money. On the other hand, find a seasoned older guy who doesn't have the "fuzzy mittens" approach to people.
There is always the option of just laying it out there. If she wants a career as a pilot, she is not going to get there with this attitude.