Seeking professional help on sleeping disorders, psychologist taught me to relax, and I fell asleep in her chair at 2 visits. Why did she charge me for that time?

Therapy Q's. Effective therapy practices are transparent. I encourage you to address any questions/concerns with your psychologist so you two remain on the same page. Also sounds like the relaxation training is working.
For solving issue. You are being treated by a professional and paying for her prior education, experience and expertise. If your problem is being addressed, why would you not want to compensate her?