I certainly sympathize! I cried for two years when I lost my pomeranian Chip. They become your family human or animal. I hope the diet works and you won't have to go throught the surgery with her!
My daughter's lab ate a whole bunch of toys and had to have surgery or she would die from the blockage caused by the toys (toy car toy tree toy doll-dumb dog!!) and it cost them $900 they agonized over it because they couldn't afford it either. The vet worked out a payment plan for them. Vickie (lab) was only 2 and she is a service dog for their autistic son. It was a bad time!! But she is better now and we just have to be watchfull she doesn't eat toys!!
Hope all goes well for you and your beloved cat!!!