I read somewhere that babies who are 6 mths and above should start taking solids as breast milk alone is not enough coz they need some proteins/vitamins to grow strong and healthy. And by then, babies would naturally develop an interest to eat. As for allergy, try giving the same type of food for about 3 days to see any negative reactions. Always introduce new food item one at a time. It's always better to compromise with the nanny. It will be more heart pain if she feed your child behind your back. You will never know what goes into your baby's mouth. And by now, it's ok to give a bit of plain water as well. But do tell her than breast milk is definitely more nutritious than FM. Many old folks are not well informed of the benefits of breast milk and some even find it troublesome to thaw the milk and heat it up.