Elderly rat with large tumour. It is time to have her put to sleep?

Hi Rachel, personally I would have her put to sleep as they will pretend to be happy just for you believe it or not my beloved Max had three tumours the last of which proved too much for me, so I had him put to sleep and I am still devastated there weeks on. Its entirely up to you but see how she goes and if you feel she is happy and you are comfortable then let her live out her final days giving you the endless joy they give. Good luck!