Hiya Martin.
Me again.
Firstly, don't worry about moaning - partly what TP is here for, to give people the space to have a good moan, knowing that those who are reading will be sympathetic. We all do it!
Right, lets try and see things from your MIL's (will refer to her as that cos it is shorter than partner's mother) point of view. She knows that she is getting older, and she is aware that she is getting a bit forgetful, but that happens when you get older. Admit that you may have dementia, you are going to 'lose your marbles', (and all those other euphemisms people use) - wow that is too scarey , can't be happening to me!
"irritable and can't do a lot of daily tasks she used to be able to do" - think about it. I remember when I first witnessed my mum having difficulty dressing. The thought that she had to put into just putting her clothes on in the right order. Imagine how you would feel, totally worn out mentally by the simplest of things, yet knowing in your heart that you should be able to do them.
And now daughter and partner have moved in. What must be in her head? 'Do they think I am stupid, incapable? Why are they eating my food, sitting in my chair, who is that man, are they going to steal?'- these aren't rational thoughts, but things that seem to go through the minds of people with dementia.
I don't know if you and your partner have done the right thing moving in, but if MIL cannot cope alone, then help has to be provided in one way or another.
Do your best to support your partner; watching your mum fade before your eyes is so painful - and she will feel torn between you and her mum. Try not to argue with MIL, it may well be that her brain is beyond reasoning. When things get tense, try distraction, or walk away from the situation, sometimes just humour her. Before escalating the tension ask yourself 'Does it really matter?'.
Don't know if that is any help Martin. You are in for a tough time, but it does have good bits. I suggest that you find out all you can about dementia and its progress. People on here will be able to tell you what types of help and support are available. Bye for now.
Helen