Oh poor you, I fully understand how terrible you must feel.
Would one of these help. Another AB user has ordered one on the recommendation of Lankeela
http://www.amazinghealth.co.uk/comfy-collar.ht m
There is a phone number and perhaps they could get one in the post today for you by special delivery. They sound really excellent.
As for the food, don't worry too much because dogs won't always eat what the vet prescribes. If I were you I would cook her some plain rice and chicken (dogs usually love it) and add some cod liver oil to every meal. A teaspoon or two to help her joints. You could also try glucosamine tablets. (You would have to find out the correct strength, but I know animals respond well to it).
Meanwhile, all I can do is to say keep your chin up and give her loads of affection (which I know you are doing) and don't feel guilty about the op. You are doing your very best for her.
Take care - both of you
xxxx