Not all JWs are evil, and sometimes you can have a decent professional relationship with them. You're not friends, you are her customer. It sounds as though she has good boundaries. If you are trying to plant little seeds of doubt in her, I think you might not be honoring the professional relationship. Her religion is her business, your religion is your business.
I don't really want to be negative. I'm glad you have a good relationship with your doctor and that her being a JW doesn't hamper the relationship.