Hi OP - I’ve only read about half of the replies, but you’ve had lots of excellent advice. It’s very difficult. My DM has been unwell for 3 years, lives alone since DF death, now has v poor mobility and is in palliative care. I’ve always been very close to her, she was a wonderful DM and DGM, but has changed so, so much due to illness and bereavement - she’s not really the same person at all now.
As a rough estimate, I’ve taken her to over 200 medical appointments during the last 3 years, which ultimately cost me my job - there’s simply nobody else so it all falls on me. It’s very stressful and ultimately I’ve had to put in boundaries and be very firm with her. It’s not something I ever would have imagined, but it was essential to clinging onto what was left of my sanity.
I realised that it didn’t matter how much I did for her, it would never be enough. It was freeing, because I could literally flog mysef to death and she wouldn’t be satisfied or happy - so there’s no point in even trying! I can’t make her happy - it’s not possible and it’s not my job. DM can be extremely selfish, self absorbed and entitled, but then a glimpse of my lovely mom shines through and we have a laugh and I know that she loves me.
Now your DM is a different kettle of fish altogether. You never had a good relationship and she’s vile to your DD. If she has narc tendencies then you’ll simply be a tool to use as she wishes/manipulate to achieve her goals. Your DC are so young and need so much of you - you simply cannot carry on as you are. It sounds like she wasn’t bothered about you until she needed a ‘carer’ and you could be useful to her.
Worst case scenorio, imagine in X years time, you decided to prioritise your mother at the expense of your family, so your marriage has ended, your DC have been side lined, you may have lost your job and your mental and physical health are in tatters. Is your DM happy now? Do you feel less guilty now? Was it worth it?
Of course not! She doesn’t even sound like a nice person - she’s manipulating, guilt tripping and gas lighting you - which sounds like emotional abuse?
My GP gave me antidepressants and said something useful - that my DM is essentially a sinking ship, the cancer will kill her, and it doesn’t matter how much water I bail out the ship will ultimately sink. The question is - and the only thing I have any control over - is will I go down with the ship, or will I save myself? It’s brutal, but it’s the bare bones of the issue. Save yourself OP.