Hi,
I wonder, is there a history of allergies or intolerances in your family or her dad's? Does anyone in the family get asthma or eczema? Is anyone coeliac? Is she breastfed?
At this age she needs meat vegies, cereals - normal family foods. She can have a good dollop of olive oil or butter if not dairy intolerant in it all. But don't stress. Petite is Ok - we spend the first years of their life fattening them up and the rest of their life thinning them down.