One thing that I have always believed in is that to truly
help someone, they have to want to
help themselves. I guess being, untidy, or even hoarding is one thing, but when the situation become unhygienic - there's definitely a problem that needs to be dealt with.
Do you have family members that feel the same way? Can you 'gang-up' on her (for want of a better term) and have a family meeting to try to show her that she needs help?