I have a three legged cat....?!? But not the advise you were looking for, the lovely Jay, Happydog, Marblemolly and Jann have already given you their experiences which i am sure will help you no end 
I have one armed OH ....?!?

I asked for his expert advice and he said 'She'll get used to it, it'll take a while but she'll get used to it"
I think he has a point. As the others have said they are resilliant, adaptable, tenacious.

I don't want you to think i'm being insensitive by being light-hearted but I bet in no time at all she'll be tearing around like normal and tumor free and you'll be so happy that it was 'just a leg'.
I know it must be a horrible time right now and there will be recovery but you'll still have your Grace and she'll be pain free and happy when she is healed, that's a pretty good deal
