If she has a gastro bug, the milk will make it worse, and run through her very quick. Generally though when they do have one, they are turned off their milk a little instinctlively.

Most doctors in this instance will recommend the Brat diet, which is bananas, rice, applesauce and toast to give them some sustanence, you can also try watered down hydralyte.

As long as she is hydrated this is the most important thing, if you are unsure you can always call health direct, they are great.