A) It’s not your house. You can make a compelling argument for shared spaces, like the bathroom and kitchen, and if you’re paying rent, you have a much better case.
B) If your mom really is a hoarder or has hoarding tendencies, just about the most damaging thing you can do is start going through and getting rid of her stuff without asking.
Things you can do that will probably get no objection/resistance: dishes, kitchen surface cleaning, bathroom deep cleaning (as long as it doesn’t involve throwing things away), vacuuming/dusting, taking what has already been determined to be trash out. Beyond that, you’re going to need buy-in, or, at the least, permission before you start messing with her stuff.