How to get my mom to stop?

My moms a hoarder and doesnt clean as much. Its been that way my entire life, i clean and clean and it always end up the same. I dont know if it's just her combined depression and my grandmother being such a neat freak thats triggered it for her. As i got into my adult years I got tired of it. I could never invite friends over, could never have anyone around do to the disaray of my household. I try not to get frustrated but i'm losing it. I moved pretty far and like to keep my place neat, if something doesnt serve a purpose i throw out or donate. I came back to visit after moving out a year ago and its just gotten worse. I tried to clean the kitchen got it spotless and told her to try to keep it clean and when i came back home after a few months the entire kitchen was trashed again. I do have a therapist who i speak with and while i've tried to bring this up to my mom my entire life she gets defensive/hostile. She knows the state of her house and gets upset and talks bad about herself. I just wish she'd get it together. I'm stressed slightly cause she wants to take care of my grandmother who has alzheimers and wants to retire but the state of her house and mentality is gonna suffer i can already see the future and it just looks grim. I don't live close by so i cant help out and im just at a loss at what to do. I'll take any advice