Its time to become more assertive. Tell her what the situation is and how it is going to be handled. Stop leaving it open ended. You need to be able to convince the customer that you are qualified and you are the one with the information regarding times and treatments. Reverse the role and get her in your back pocket. Do not walk away from a customer regardless of how much of a pain they are. Once she understands you are the one taking the reins then the questions from her will soon become compliments. Business 101.