silencing a home AC unit?

Put wind chimes above it maybe. That may help or it will just annoy her more. My daughter is very sensitive to sounds too. So I know what you’re dealing with. I also have my mother in Law living with me a we moved the AC Unit when I added on a room for her and we put it away from the window. I don’t remember how much it cost me. Unfortunately what usually happens is when you remove that noise a new noise is coming.