Nomad,
This is so difficult but I'll chime in and say I too agree with not paying her. I think your gesture was kind-hearted. Your thinking was but for a moment as if you were dealing with someone rational and logical. I often forget that too with sons. I've tried to do something along those lines that would motivate most but then it always back fires on me. And why? Because my sons are entitled with mental, emotional issues, anger, resentment and the list goes on. I've tried so hard to have a "normal" relationship but then reality rears its ugly head and I remember that's not possible, at least for now.
Glad you're in self-preservation boundary mode. I'm in that club too.