I am not sure if your weight measurement was 16lbs or kgs. If she is 16kgs, then her weight is on the 25th percentile for her age and she is normal. Some children are smaller then others in the same family. Thank you for your question.
Your daughter not interested into food? I think not. If she do not want to eat then you do not create pressure to her. When she will feel hungry then she will eat. I think interest of food increase the weight and health.