mum is a bit of a hoarder and idk what to do

my mum has always had a little too much stuff for one person, and since university when i moved out, it's definitely ticked upwards

i also read that hoarding can often be triggered by trauma/tragedy, and that's relevant here as well

for an idea of the problem, she has a reasonable 3-4 bed house (even though it's just her), and only the master bedroom is still habitable. the kitchen/living room/hallways are also all very full

she suggested i share a bed with my brother when i come home at christmas because my old room (which i last slept in in May) is swamped. at some point, the house will become largely uninhabitable/dangerous to move around (although it is at least clean, just FULL AF) and she's obviously going to get less mobile eventually

what exactly can i do? i've told her she's got a bit too much stuff, and on the one hand she comes off as slightly embarrassed, but mostly it's as though she sees the post-covid world as a need for intense survivalism for when the supermarkets inevitably become deserts (/s)