Hello and welcome
@Warby76 to this friendly and supportive forum. There is a lot of shared experience of dementia here and members really do want to help.
I am sorry to read about your Mother and her worsening dementia. It's a cruel disease for sure, and for you all as the immediate family, it is so tough. I do feel for you.
Often, people with dementia deny there is anything wrong with them so why should they need help....so accepting help when offered can be very difficult. I'm sure she would rather you four are able to do a bit of helping and supporting, rather than other carers/strangers coming in. But it is certainly a difficult one to get around.
On a practical note, while your Mother still has capacity, and it sounds like she does, do start organising Lasting Power of Attorney for both the health and welfare one and the finance one. This will make things easier for you a bit further down the track. This link may help:
How to make a lasting power of attorney (LPA): starting an application online, choosing an attorney, certifying a copy, changing an LPA.
www.gov.uk