That's odd because Wellness is an excellent food. There are other brands that are also very good too though and maybe you should try switching to one of them. She maybe allergic to something in that brand that is causing the problem. There is a brand called Blue Buffalo. It is excellent also and they have both dried and wet.
Its good by the way, that you are feeding both as cats need to get more fluid from their food. In the wild they get 70% of their fluid intake from their prey.
If she still has problems after this switch then what I would recommend is to feed her people food in place of the wet canned food and continue with the dried kibble from either Wellness or Blue Buffalo.
You can use chicken (dark meat is better than white because it contains more fat which they need), chicken livers, some fish (careful of bones though), canned salmon, canned tuna in water, I even mix sardines and salmon together and they love it. I boil the chicken and the liver and I simmer any fresh fish in water. Feed the same amount you would if it were canned. As long as she remains on the kibble and this too you will not have to worry about supplementation.
I'm new on here, so just for the record...I was a vet asst. for 15 years and a cat and various other animals Mommy my whole life. Good luck and I hope this helps you. God bless, Sharon