I remember reading a young adult fiction book some time between 2000 and 2010, where one of the characters was some kind of witch who was hiding out somewhere. She couldn't do very strong magic but would frequently use things like "look-away charms" that would cause whoever was near to look the other way without realizing, and she would use this to escape notice. I think this was referred to as "hedge magic" At some point a boy (or man?) comes looking for her, and she ends up imprisoning him in a shack, but they become friends somehow. I think she used copper or bronze to imprison him because she could not touch iron.
At some point, there is a sequence where she speaks with the boy from on top of a wall (a ruin?) and then causes him to look away, before hiding and escaping his notice. A plot dynamic seemed to be that the boy (and others) viewed the girl as a powerful and dangerous witch, but from the girl's perspective she was limited in her powers and more afraid of everyone else.
The world was a low-tech medieval setting, and magic seemed to be uncommon and frowned upon. If I remember correctly most of the plot happens in or around the witch's encampment, which was in the woods. There was some kind of kingdom referred to but I don't remember it being visited during the plot, although maybe I just forgot way more than I think I did.
I can't remember what the cover looked like but at the time I was reading a lot of young adult fantasy literature like Heir Apparent and I think it blended right in with that style.