I was interested in how Mindsin would suggest you make it "your" boundary. A personal boundary is not about controlling the other person.
That would be like saying that her lying to you is a boundary. All you can do is control how you will react to her action. But you can't control what she does. You can tell her all day it is a boundary, and she could laugh in your face and keep telling you lies. Then what? What do you do when a person doesn't respect your personal boundaries? That's what you need to know.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!