This rang a bell with me and a did a quick search and up came this correspondence from five years ago.
Now the circumstances aren’t identical but there are similarities. So what should you do?
First things first, the smell is a nuisance and the accumulated rubbish represents a potential health risk. You would have grounds for getting orders under section 117 but that would be a lengthy process that could take two months, including a mediation that she probably won’t attend.
Alternatively, the EC could serve her with a notice demanding the place be cleaned out within seven days (offering any assistance you consider appropriate) and if she fails to do so (as she will) apply to NCAT for an interim order (S.170) allowing the EC or its contractors to enter the premises and clean the place out.
Before you do that, try to find a local health visitor or aged care visitor who can be there when this is happening to minimise the distress. in extreme circumstances, if there is no family there to look after her, you might want to look at legal guardianship services.
Best of luck