I would put her on chicken and rice straight away, and keep her on it until her tum has settled down completely. White rice is better than brown actually, in this situation you want things as bland as possible.
We had similar problems with our Jess - several episodes of colitis - it took us a while to twig that she didn't get on with wheat. Besides, of course, the transition away from mum and littermates, which is stressful to start with.
By the way, if you are not happy with the food that the breeder was using and are planning to move her to a better one, then that should wait until the little one's tum has settled.