I live abroad and my mother retired to a spot in a UK village, 15 minutes walk to the nearest bus stop. Fine when she was in her 60s and loved walking but useless in 20 years later unable to drive and mobility issues. She refused to take taxis.
Her neighbour's were an older man, young wife and teenage daughter. My mum had babysat the daughter for years, went to her school plays and concerts etc. The wife had to return to Poland to nurse and bury both parents over the three years.
Popping round to deliver gifts on a visit back the wife told me 'I like your mum and she is like a grandmother to XXXX but I have cared for sick parents and buried them. I am NOT doing it for your mum, so I have distanced myself'
I told her I completely understood. And I really did. Another relative was furious but mum was not her responsibility and although blunt I admired her honesty. The husband would look in on mum, help with shopping etc - call me if there any issues but the wife stayed well away.
Eventually, my mum went into a care home as her dementia progressed. The wife wrote me lovely letter which I read out to mum. They still drop off cards at the care home and I return cards from my mum.
Your neighbour has seen you 'care' for lots of people around and assumes you like it/ want to do it. I would set your stall your now. You don't have to be as blunt as my mum's neighbour but you sound like a lovely person and you can't afford to be vague. Do you know her closest friends in the village? Do you have a number for a relatives? Is she a member of a church?
They can be helpful. Tell them - you are not taking on her caring responsibilities. You are planning to take holidays, get your life back, still grieving. Then you need to tell your neighbour - that you are unable to help perhaps she can ask ......... then she is not left high and dry but you can enjoy the life you deserve.
Good luck OP