She eats little and you try to feed her frequently.
Be patient and pay much more attention to her, maybe she will be better when she grows up.
Same as me. My daughter is 3 years 2 months old, she is thin and small-sized, eats little and sick frequently (almost once a month). Just try my best to take care of her.
I always tell to myself and my family that she will become strong and better afterwards.