I am sorry your mom is dumping so much stuff at your house.
Have you ever read the book The Five Love Languages? Maybe her love language is gifts?
If it is and she is showing her love for you by giving you stuff, maybe you can get her to give you usable stuff ( food items, nice soaps, annual garden plants or flowers, etc.) things that get used up and don't take up space in your house forever and ever.
That way she can give you things that will get used up, so she feels like she is showing her love. You can use those items up and they are gone.
If she insists on giving you things you don't want, tell her that you are going to donate anything she brings over that you do not want, then do that. She was told, so when you follow through and donate the unwanted items, she can't say you didn't tell her exactly what your were going to do with those unwanted things.