Thank you for sharing your journey with your lovely Mum. On the same path with mine, but not as far along. I try hard not to go down the 'dementia is so terrible' route in my head as it feels so dreadful and thinking like that ends all hope and terrifies me!
I just concentrate on what I can do practically day by day. I don't look at my Mum and think she's not her real self, just that this is a new stage in her life - she's very vulnerable now, sometimes emotional, sometimes snappy or anxious, often increasingly detached and tired. But as I say, not so far along - five years post diagnosis, so I don't know quite how bad it's going to get.
The only experience I can give is with the food. I was once in hospital for a week, after which the infection cleared up, but I was left with 'loss of appetite'. It really was impossible to contemplate any food and the hospital took it very seriously and kept me in until I could eat normally again. So I can sympathise with my mum and yours a bit - if your appetite has disengaged, you simply can't physically bring yourself to eat.
If all she'll eat is a few spoons of porridge and Fortisip style milkshake drinks, it may be enough for now - my Mum regained lots of weight on them. You can also get fortified fruit juices and a few other things from the same brand. I've also seen jelly sweets that help hydrate dementia patients and my mum will try very small easy to eat sweets like white chocolate buttons, milky way stars etc. I think these tiny snacks help as nobody says they must be eaten here and now - nothing for the dementia obstinate streak to flare up against!
Thanks again for your updates, I'm sure they've helped a lot of people..