I just saw this website called SqualorSurvivor, and the stories these people had were horrendous. Perhaps
you could alarm her with this type of info. People sick from the mold, unknown filth hiding in piles of hoarded things?? Often a professional needs to step in, I suppose, because of the emotional personal attachment of it being a family member.

No, you are not nuts.

You are a good daughter who is frightened for your mom, and frustrated at the situation.

Don't get rid of any of her stuff. When she finds out, her trust in you will be broken, and things could get bad.

Instead, try talking to her doctor. Maybe even take in pictures to convince the doctor of the severity of the issue. There's growing evidence that hoarding, as opposed to just being a clutter-bug, has some basis in a mental-health issue, and possibly OCD.

Do some research on this before talking to the doctor, in case the doctor isn't educated in this. It is possible that there is treatment out there for your mother, that would allow her to start letting go of the things.

You could try the rational route, and point out to your mother that if she falls and breaks a hip, there's a good chance she'll end up in assisted living or a nursing home and then she won't have any of her "stuff," but I've tried that and it didn't work. Getting my father on a very small dose of a mild anti-depressant--that worked.