Would you be weirded out if someone sent you a thank you note for being a good parent?

There is nothing wrong in any way to do what you want to do and I am sure she will be impressed by your efforts. I know if it were me on the receiving of a note like the one you want to send I would appreciate it. I am sure that for her it is difficult some time to deal with issues like the one that she deals with. To receive a note would show her maybe that people recognize her situation and she is not alone.