I'm going to ask my mom to stop humming in public
How will you ask her to stop humming?
I'll ask her to not do that in the future.
You shouldn't be telling your mother to stop humming as that is seen as controlling. If it is truly such a problem, you could put on some earbuds and listen to music or something.
I shouldn't have to wear earbuds to ignore her humming. She should stop because I said so.
No one, especially your mother, is beholden to your wishes so you will have to deal with her humming because most likely she would ignore you.