how much does your vet know specifically about chinns? generally fresh greens are not OK for chins, unless you meant that the wheat was dried, but fresh... a lot of veterinarians only get about a week of schooling on small animals, that's it, and usually only general stuff, chins are different than many small animals, especially when it comes to diet, there little digestive systems are built differently than an average rabbit, hamster, guinepig, etc. most of those will be able to eat many of the same foods, but with chins you have to watch, chins come from a cold, desert environment in the Andes mountains, so most all of there food is dried out, they cant handle the wet vegetation most other small animals can.
a chins diet:
-plenty of clean water is a must for any animal, even if they don't drink much of it,
-dried hay, the greener, the better (as opposed to brown) as much as they will eat
-pellet food, provides vitamins and minerals, make sure to check out the dietary facts often listed on the back, I was very annoyed once to find that "Pro Diet Compleat Formula" was not as complete as the label claimed: about 2 tablespoons is a good amount. if you get one that looks like it has treats in it but is good nutritionally, don't go and pull all of the "treats" out because some tell you about moderation of treats, they do not count as treats. they have vitamins and minerals in them, and they have some way of removing the sugars from dried fruit pieces... ask anyone who has tried sampling a piece of dried fruit out of there chinns food, they taste TERRIBLE (yes, some of us actually tried it)
that's about it for regular diet... raisins and rolled oats (not quick cooking oats) seem to be the safest as far as treats go, although dried apples are also good, and many say rosehips are also a good treat... dried bananas...
*AVOID ANY FRUIT WITH A PIT!!! these include peaches, apricots, avocados, and many varieties of pear, fruits that have a pit are very poisonous to chinchillas
treats one or two a day is usually good, depending on the size, one raisin = one treat that holds true for most dried fruit, about a raisin sized piece = 1 treat