We had FiFi put to sleep today, it was a hard decision to make but it was the right thing to do. She wasn't going to get better and we could see her condition was starting to deteriorate, she had stopped cleaning herself and seemed to have very little energy.
It's a real shame but at least she had a good life for the four months she was with us and has been spared any pain or discomfort.
We still have her sister, she's massive and full of life.