Don't worry about her not ever wanting veggies if she has fruit first. I had a LOT of people tell me this, of course AFTER wiz had already had fruit, lol. All my kids had fruit first and they ALL eat veggies and always have. my kids actually like veggies FAR more than I do. I eat them because I know it is necessary, but I don't like very many no matter what you do to them.
Back off for a week or two. Pushing is the worst thing you can do. A week or two of just formula at age 6 mos isn't likely to be a problem. Given the kidney issues, it would be better to back off a bit and let her adjust and then start again rather than to keep pushing and have her end up totally refusing for a long period of time.
The feeders can be helpful, esp if problems keep her from being able to use her mouth/tongue properly to eat foods. To get cereal eaten, try miing it with whatever juice or sweet stuff she can have instead of formula.
One problem that may be contributing is that often the start of baby food leads to stomach cramps, gas, etc..... thank you is the only one of mine who had few problems with that when starting foods. We were still giving him catnip tea in the evenings with a bottle and it really works on stomach problems. If mint is not on the list of foods that cause problems with kidneys (peppermint, spearmint, etc.... - check adult kidney diets for her problems to see if mint is okay or not), then it is safe to try an ounce or two of catnip tea in her bottle of formula. Catnip is a mint plant, but not as strong a flavor as peppermint or spearmint, and much better for stomach problems (colic, etc....). The kidney doctor/nutritionist may not have a clue because few people think of catnip as something for people. It was a miracle for us though.
I hope that this is a short term problem and in a week or so she takes to baby food with gusto! have you tried sseerving it cold, or warm? Sometimes serving it at a different temperature is very helpful. Not too hot or cold, of course, but just enough that it seems different.