Thank you everyone. We feel it is the best thing to do for her, as she is only going to deteriorate and her quality of life is virtually nil. Our vet is doubtful she would get through an anaesthetic even if we tried for the amputation.
For such a lively rabbit, she is now confined in a pen in the garage. She's not a people bunny, so doesn't really like my company, and no longer has her beautiful Bobby. The least we can do is reunite her with the love of her life.