hi cider,
sorry to hear puss is frail - but it sounds like your mum might be right. this is the hardest thing to think about - and i speak with experience as my 20 year old cat had similar things happening to her when we had to have her put to sleep. i put this off for a few months as i couldn't bare to be parted from her but a conversation i had with a friend made me realise i had to take action. he pointed out that i was in fact being cruel by keeping her alive while she was clearly so ill. he asked me where was the dignity in allowing her to be in a mess and to show her some respect as animals are very proud. might sound crazy but our chat really helped. i took the step and took her to the vets and the inevitable was arranged. it was so sad - even the vet was crying with us - which really touched me. they were brilliant with us and made the process really calm and peaceful.
also, last year my aunties cat became very thin and matted, even though she was eating - she had her up days which kept giving us hope, but then she'd be down again. When we took her to the vets it turned out that she did have something wrong with her and needed to be put to sleep.
hard tho it is, think about what my friend told me - are we being cruel by hanging on to them? there are some beautiful poems and words here on answer bank from animal lovers - written from the perspective of the pet - please read them and you might feel easier about this - i will go and find the link for you now and post it here shortly.
keep us updated - there are loads of friendly people on here who will chat you through any difficult times.
bestest wishes
xxxxxxx