Very sad - she was her usual chipper self yesterday but this morning was lying on the ground trembling. 
Rushed her to the vet who said she was full of tumours and we should have her PTS straight away. Complete shock as she showed no outward signs whatsoever, until today.
Anyway, now of course I'm worried about the other one! They did their own thing really but will he be lonely? He's really unfriendly, unlike the other one who was really affectionate, and he won't let anyone get anywhere near him. He's quite keen on the dog, bizarrely, but humans - forget it!
Should I get another one. I don't want to particularly, but is it cruel to keep one on its own?