My mother in-law isn't a hoarder, but she has a lot of stress and anxiety that makes life difficult for her and those who care about her, and I feel bad for how difficult this is for her. I think she would benefit a lot from CBD gummies or something similar, but she has a lot of religious scrupulosity about that sort of thing.
I'm not sure what I would do in your case, but I'm glad she has someone trying to help, and hope you can figure something out.