I was in the same situation last year, my old boy had epitaxis and a tumour in his nose. The prognosis for it was 5 months - but after he had his first nose bleed, I realised where the smeared blood had been coming from for the last few months along the side of the settee, so I treasured each day I had with him. We had the vet out to the house as I didnt want to upset him to take him to the surgery and he just took one look at him and knew what it was as he said the side of his nose was slightly distorted, which even when it was pointed out we couldnt see it. He treated his symptoms systematically as he was far too old to have such invasive surgery, and even though his nose bled when he was eating, it didnt seem to bother him and I just wiped it away. On his 14th birthday a few months before we lost him, I bought him a ready cooked roast chicken and fairy cakes, and did he enjoy it.
He was my shadow, and my husband was dreading the day we would have to say goodbye as he thought I wouldnt be able to go through with having him put to sleep. But to be honest when he woke me up in the night in pain and was unconsoleable I knew it was time, and although I cried uncontrollably, he was in my arms right until the end (OMG I am crying buckets writing this!!).
You love your little girl, and will do the right thing for her, my thoughts are with you, take care x