Haven't updated in a while...
Lolly went back downhill over the weekend as I thought she might. She was back at the vets Monday morning and when the vet examined her again it was becoming more obvious what was wrong with her; her eye lids and gums were pale yellow, indicating jaundice. A highly positive result on the lipase test she had done and an ultrasound which showed a lot of inflammation around the area of her pancreas (and bile ducts) suggest she has pancreatitis and Lolly has been staying at the vets since.
Lolly has been on a drip constantly and has been given pain relief and medicine to stop her feeling nauseous. She's still not been eating properly for days, only picked at her food, probably because the inflammation is still causing her discomfort and she's a bit anxious about being at the vets.
There was better news yesterday because she finally ate a whole bowl of food, albeit a small bowl but a whole bowl none the less and looked keen to try more. However, this morning they said she'd not eaten anything overnight again. Again this could be because her pancreas has become a little inflamed after eating during the day. She has managed to put a bit of weight back on during her stay at the vets and is otherwise looking a bit brighter anyway.
The vets said she may be able to come home again today if she's alright in herself and eats something, if not they'd like to keep her in for at least another 24 hours.
Her diet will have to change and the vet said the only thing she would eat while she was there was chicken flavour HiLife so I'll assume that's what they're going to recommend I feed her at home. A problem would be how to prevents the other cats from scoffing all of Lolly's food which could be especially important if I have to add medicine to hers...
And I hope one of my local supermarkets actually sells HiLife. xD