Sonja, I'm so sorry to hear your Mitzi girl is sick and I hope you and the vet can get her feeling better soon.
When Tink was so sick last summer and her liver and kidneys were failing, we did sub-cutaneous water and it helped her enormously - but again, she was really sick and could hardly drink. That's when I started her on home cooked broth and home cooked meat and vegetables, mostly chicken and beef. My vet wanted her on Science Diet, but I didn't want to put her on it for the same reason - corn allergies. The vets at the emergency hospital were all in favor of home cooked.
I'm sure there are some on YT that can help you more with Mitzi's needs. I'm sending up some prayers for your special girl and you.
