My cat has crystals in her urine that built up and made her bleed in her pee, now the vet says she must stay on a vet prescribed cat food they carry, but its a pretty penny. What else can I do or is there any cheaper brands or could I mix some of her old dry food w/ the vet one? I love her and hate to sound so cheap, and I want her to live a healthy carefree life, so just wondered if anyone else had same issue, any advice helps!