Meaning of persistent diarrhoea is different for doctor than parents. If you have mentioned about No. motions in a day, quantity of stool, consistency, either with more water or feces, containing mucus and / or blood. related with dietic habbit. it would have been easy to suggest. Any way, if her wt is about 11 kg, you need not to worry. Give her food of her choice and sufficient quantity of water to drink insist forcing ors etc.