If you are questioning (and your opinion/view is all that matters with your therapy) then it probably is not a great arrangement and certainly sounds "painful" to me. With therapy, you should not have to be confused as to the relationship, you should be able to discuss it openly and equally. The therapist already has a bit of a power advantage since you are wanting her services but to be less than straightforward with the payment and able to adjust times, amounts, etc. without discussion with you does not sound very kind and slightly "unethical". You are indebted to her and that's not good for therapy. There should be an agreed upon fee for X services and it should not be adjusted without both people's input.