I'm no nutrition expert at all. ;) I just remember that the only reason my instructor TOUCHED bran mash(for the ratio issues) was when we had a mass colic outbreak from foxtail in hay.
Can you call up another vet for their opinion?
If I were you, I'd call up SmartPak for their help. They have a lot of digestive supplements, but remember, sometimes you simply CANNOT prevent colic episodes. I'd put her on a joint and tummy supplement. Joint supplements are pretty commonplace.