I do agree we go to her looking for help so it is fair we give something in return, and she doesn't 'force' us to do anything but like with the werewolf thing she was already familiar with the process and effects that using the cure had but she actively withheld information, she knew, was important and leveraged it to gain an open ended favor that can entail anything, going as far as refusing to share said information with you if you refuse her proposal while also knowing she has a monopoly over this knowledge. Which doesn't paint a good picture of her seeing as she took advantage of a desperate moment from the herbalist to profit in some way. Same with the mind protection but I still got it anyway because when shit hits the fan I want to have at least some form of protection, and those favors will come back to haunt my nightmares some day mark my words.
Side note: agree that with the nameless we at least expect him to be a jerk, so it will catch a lot of people by suprise if she turns out to do something bad, but I don't trust that woman