A welcome from me too
@LesleyS to this friendly and supportive forum. There is a lot of shared experience of dementia to be found here and members really do want to help.
I am sorry to read about your Mum's recent diagnosis. It's tough for sure, even if you were half expecting it. You will know , I'm sure that this is a progressive disease, so now is the best your Mum will be. You have your own family/husband and you do not want your Mum's condition to cause any sort of family breakdown. After all, your Mum wouldn't want that would she.
Maybe its time to get Social Services involved to do a care needs assessment. I think you need extra support. This link may help:
What are care assessments and how can people with dementia and their carers access them? This information is for care and support in England.
www.alzheimers.org.uk