I have struggled with my home over the last couple of years. Partly hoarding. Partly an increasing number of things that need doing and the overwhelm that comes with that. Working full time. The feeling of shame. The fear of being judged. I subtly stopped any visitors by hosting birthdays at parks or beaches or local venues, always being the one to offer to drive and meet elsewhere for meet ups, going for a walk for a catch up with friends rather than having them over for a cuppa etc. If anyone had noticed how bad it got I'd have been mortified. If help was offered I'd have felt a deep hot shame.
This year we had an emergency reason for work on the house (not related to the mess and hoarding) and have had to clear the whole place for various trades to do their thing (plumbing, roofing etc). I had to accept help from my closest family as there was a time limit and huge costs involved. It was painful and stressful and I feel sick and panicky just thinking about it.
I don't know your mum and I don't know her exact situation but I do know that the process of emptying the house and storing things temporarily in a family member's house, shed, garage, loft AND having people help with sorting through things, skip hire, tip runs, and my endless charity shop drops and getting things sorted for vinted and facebook marketplace has been hellish. It's been humbling in the worst way.
On a more positive note, I do know that things will be better when our house is ready to move back into. And the decluttering I've been forced to do will help to keep it a nicer space when we're back in and can redecorate.
I know mumsnet to be the least empathetic and supportive place I've ever experienced and I'm prepared to be called filthy and gross and evil and cruel and lazy and useless and whatever else it spirals into and that's the stuff that keeps people like me from letting other people inside and from accepting help before it gets to a desperate situation. Because I already feel all of those things inside even when I'm able to present a capable, put together, professional, helpful person in all situations OUTSIDE of my home.
I don't know if your mum's a hoarder with mental health issues or if she's just got too much stuff and is overwhelmed. I don't know if she doesn't care about what it looks and feels like or if she cares too much but can't even begin to feel ready to tackle a tiny bit of it or accept help.
Personally, I benefitted from the couple of people closest to me who came and physically got stuck in with no judgement. Who took boxes and bags of stuff and offered to sort through and donate. Who've helped me think positively about having a fresh start and choosing paint colours. Who've acknowledged that it's not easy and that they know I'm struggling.
The big kick up the bum was the house disaster that made it an emergency requirement.