Her weight is between 5-10th percentile and her height is between the 50-75th percentile for her age. She may appear thin due to her stature is higher than her weight; however, she is within the growth chart which indicates she is normal for her age. At 3 months old you can start to give her infant cereal. Here is a guideline for an 3-6 month old child should eat the following on a daily basis: Breast-milk or infant formula (2-4oz) 8-12 feedings per day, Infant cereal (1-2 Tablespoons) 1-2 feedings per day. Give the rice cereal by spoon. Mix the infant cereal with 2-3 teaspoon (or more) formula and/or breast milk until a good wet consistency (but not runny). Increase the cereal as the months go on. Hopefully this will help with weight gain. Suggest relaxing when you feed her. Infants pick up on tension. If she does not drink then do not make a fuss and see what happens the next time. As you relax, she will eventually drink and eat the cereal. Hoped this helped you.