Just a tip so you can get a good feel of whether or not she is dehydrated - pop up folded up tissue in her nappy. If she does urinate (even a little bit) you will know for sure because the tissue will be wet even if the nappy doesn't feel wet iykwim (sometimes it can be so hard to tell). We had a similar thing with DS a few months ago and the MCHN hotline gave me that tip. The other things they told me were if there is no urine in an 8 hour period take him to hospital, and other less know signs of dehydration include cold hands and feet and dry mouth.

With the gastrolite/pedialite I found that giving it to DS in a dropper was about the only way I could get any into him. It is tedious cos you can only get a few mls in every few minutes, but I tend to think every bit helps. It is good stuff because it also keeps the bodies salts etc in check.

I know the docs say to steer away from milk and dairy products when you have gastro because there is a small risk of it leading to lactose intolerance in the longer-term. I'm not sure how old she is, but if milk is a key component of her food intake normally then I personally don't think giving it to her a bit can hurt, after all at least it is a fluid.