Chinchilla food with treats in it (ie: corn, bananas, raisins, and colorful puffs) is absolutely worthless to a chinchilla's health.
In general, they are very picky eaters
and as long as they're not starving they will pick the treats out of their food bowl and leave the 'yucky' pellets behind. Alot of pelleted food that petstores have for chinchillas don't have the essential nutrients to keep a chinchilla in good health. Chinchillas have a very sensitive digestive system and often diarreah will result out of a poor diet. Obviously diarreah can lead to worse problems and high vet bills.
Aside from getting a healthy pelleted food, like Mazuri
(which is what I fed), it is MUCH cheaper than the petstore brands of chinchilla food.
Make sure that if you so decide to switch her diet to a healthier pellet, do it slowly. With such a sensitive digestive system, switching it too quickly can give her tummy aches and promise you some diarreah nightmares!!
Then she'll have poopy fur. hehe, it's happened to me.