Dogslovelakes I know exactly how you feel. I am going through a similar situation and struggling to find a solution. It is not feasible for me to drop everything at a phone call to sort out emergencies which are frequent.
I have had to employ a carer initially without Mum's consent and the carer does the shopping once a week. I no longer do it. Mum will not starve as food is brought for her but it no longer involves me. Interestingly this has been set up for a couple of months and she loves her Tuesday afternoon outings with her carer to the big Tescos!
I have just this week organised a daily carer to pop in. Mum is now kicking against this saying she does not need it - I have said I need it.
Harshly I have not contacted her for two days as I had to have the space - she has seen other people and I know she has all she needs. Today I got the emotional phone call that she is all alone while everyone else in enjoying themselves having turned down an invitation to go with her neighbours so her loneliness is her choice.
I find this incredibly hard to do as I will bend over backwards for anyone and everyone so I feel that I am being hard on my own mother. However I will be dead before her if things carried on as they had. Also my own family suffered as I had no time for them, had to cancel plans etc due to situations with my Mum.
Also I feel that she gets more stimulation from seeing other people than just relying on me.
However this is work in progress and I know that there will be another emergency.
On a practical level can you sort out Meals on Wheels - they will bring a hot meal and sometimes even sandwiches for a second meal. Just book it and say you are not able to come every day - do not give a reason just that this is going to happen.
In my experience once one thing has been sorted out there has been another thing that only I can sort but again outsource this. Keep your visits for social only.
You must not sacrifice your family holidays etc for one member of the family when there are tbh probably better qualified help available. (That was meant in a nice way not that I think you are incapable just giving you a reason to let someone else do it
)