Hello
@jude1223, welcome to the forum, which I hope you find to be a friendly and supportive place.
It is common for both a person with dementia and their family to suffer a grief response when a diagnosis is received. It’s called anticipatory grief and relates to the loss of the life that existed but is forever changed. It could be that this is causing some of the anger and denial. My wife refused to accept her diagnosis and riled against being unable to drive but came to accept these things within a few months. However, Canary is also correct in saying that some people are simply unaware that they have a problem. I hope it’s a matter of anticipatory grief as that will be easier for you in the long run.
When it come to relationships I have to say that you should be prepared for a role reversal as time goes by and your mum loses her abilities. I find that with my wife the relationship is increasingly parent and child rather than man and wife. It’s a strange thing but it happens slowly so you adjust to it.
Now that you have found us do take a good look around the site as it is a goldmine for information. Reading old threads can be an education and then there is the Society publications list that can be reached by clicking this link
https://www.alzheimers.org.uk/get-support/publications-factsheets-full-list
In the publications list you will see factsheets on things like the grief response and getting things like Wills, Power of Attorney etc.
If you would like to check for support services in your area you can use this link to do a post code search
https://www.alzheimers.org.uk/find-support-near-you