Jo sorry to hear about your Nan and the ongoing worries. I debated over telling you my story, but sometimes it helps to read about other peoples experiences.
When my Nan first became ill and was eventually diagnosed with dementia, she hid it really well from me. My great aunt and I were the only visitors she really had, i was the one that went every weekend to visit and did her shopping. After we found her wandering around her flat in her nightie, and she was non responsive for a while (in hospital) I realised there had been a couple of clues. She used to write me a shopping list and for three weeks running she wrote sellotape on it. I would check her fridge and veg box and found that she wasn't eating the potatoes. My great aunt who was the other visitor, said she only ever saw nan eating half cooked toast. This had been going on for a few weeks.
The day we found her stood in the middle of the kitchen in her nightie (someething she never ever did, she was always dressed), she had changed her whole room round, every ornament was on the floor and placed very careful and gently around the place, I found glass ornaments behind the tv. She went to bed whilst I rang the doctor and she just smiled at me, in the ambulance on the way to hosp she zoned out and over the next week or two she didn't speak and was very unresponsive She wouldn't eat properly and would only eat the puddings I fed her. She was in hospital for 5 weeks and eventually was discharged to a home. She had just had her 80th birthday and a lot happened in that week. I'm only telling you all this because its always the ones that are closest who are the last to know there is something wrong. I really hope its nothing and all will be well. Luv and hugs hun xxx