I have a 15 year old female cat, Meg, she'll be 16 next April. And a 7 month old female kitten, Bella, also known as the demon cat

Its my old girl Meg im worried about at the min, her urine smells very strongly of ammonia, its makes your eyes water strong, she has dementia so i have water bowls all over the house as she was forgetting where the main bowl was. Recently she also has got spots or scabs on her skin and is losing little tufts of fur.
Now some people have told me this is because of her age but i wanted more advice from other cat-mums especially if you have experience with geriatric cats.
I will whisk her off the vets if its needed, but she gets very confused and stressed out, so dont want to put her through going to the vets, outside of routine check ups etc, if its not needed.
They are both house cats, not sure if that makes any difference.