Well remember, you go to the Witch, repeatedly, for help with various things - and this is 'you go looking for help'.
She does ask you for things in return, including something open ended. But she's /tremendously/ more straight forward with you than the Nameless - the Nameless makes a bit deal of his superiority, the Witch actively helps you multiple times.
The one thing the Nameless wanted from you directly (the gem) you are forced to give him. Thus they aren't really similar in that or most respects, haha - he treats you as though he is your superior, she is much more 'You didn't come to me to read you my life's story, you came to ask what I know about (say) werewolves'.
...now I mean, some suspicion is then well warranted, as it's always the ones who aren't actively being jerks that can catch you by surprise, haha. But hey.
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
If we stop to think about both are pretty straightforward at admitting they want to use us it's just that the nameless is a dick about it with his superiority complex and the witch is more like a merchant seeking the best profit and deal for herself, but yeah I also hate he dared to threaten my friends and used Korg as a hostage to demonstrate his power. I don't think we can do more than one charm tho since she herself said that there would be consequences given we're dealing with powers not meant for humans twice so... There's that.