Canned food is definitely not bad-in fact, it’s technically better than kibble (just not as cost effective or convenient) and as far as figuring out if it’s a good food-take a look at the label. There are articles on this site that will help you decipher the labels on dog food, and you can also just take a look at the reviews of the canned food you are considering and see where it rates.
There are a myriad of reasons her stomach could be upset, so that’s a hard question to answer, but overall I would work on finding her a food she enjoys more. There could be something about the food that is upsetting her, which is why she is trying to avoid it.
