I worked in a cattery for two years, and we were considered the best in the area, but I still wouldn't have recommended putting an old cat that was ill in there. Most cats find it very unsettling and scary if they aren't used to it, if they don't bring their own food that can upset them, the medication gets done but I spend many hours having to figure out how to get the cat to eat it (since we had shifts and couldn't just wait until later on) and I suspected that some of my colleges never bothered that much. We had a special section for older/unwell cats but it was still obviously stressful for them, and if I'm honest, me too, I worried every time I went in there that one would have died and I'd have to call the owners about it.
I don't want to sound like I'm accusing you, but with the house move and considering your cats health, was it the best idea to book a holiday that was even longer than usual? If she does make it to another year that's something to think about.
I'd consult your vet, but I think queenarmadillo had the best idea of moving her in with your parents for a while if you can, even if she doesn't know the house she'll at least know them and they'll be more aware of her routine than anyone else.