Flat lemonade works wonders (as per above advice) ... It's fantastic for rehydrating . Just stir it to flatten it. My mum always tells me to steer clear of dairy other than their daily milk intake .. Until the vomits stop. Cooled chamomile tea can help to hydrate and settle them, and it tastes yummy too. Cruskits with Vegemite are a good post gastro snack.
Lucozade is good too- they sell it in pharmacies and supermarkets. hope your baby girl is better soon hugs