Oh dear this is always a terrible choice. My dad had been in his residential home for a few months and absolutely played a blinder on a locum dr who came round to see him. This dr listened to Dad and a carer, and Dad was on such good form the Dr said he had capacity. He then asked dad about DNR, and because dad thinks he's at the start of his military career, obviously he said no to a DNR!
This has since been reversed. Dad told me earlier in his life if he got dementia to shoot him, and while I don't think I'll be doing that, I did put a DNR in place later on when Dad was deemed to not have capacity. My best friend's dad was successfully resuscitated when we were teenagers, twenty years ago (and he was younger than my dad to start with!) It was incredibly hard for him to recover, he must have been in his 50s or 60s at the time, and in fact he died a few years later.
Resus doesn't often work, and it is not well tolerated and is physically destructive to the frail. It's your decision but I decided it was kinder to let dad go, if he goes. We have agreed, also, to have a case by case review, so dad will not be taken to hospital unless it's absolutely necessary, e.g. no tests or investigations for something small, but if he fell and broke something then yes of course.
If mum is not eating, is it by choice, through stress or illness or is she not needing food any more? I don't want to shock you, but sometimes people get hospitalised for not eating when actually they are at end of life and have stopped eating because of that. This is really hard to ask but can you ask someone who cares for her if they think this is the case?