My little sister is 3 yrs. old, i'm worried because she doesn't eat, she only eats like egg in the morning then biscuits in the afternoon that's all, what can i do?

Model good eating: Kids in this age group are struggling with the idea of independence & self direction which is often reflected in ignoring advice on eating. If they witness proper food selection & enjoyment they are more likely try new things (when they decide its their idea). Most grow out of this stage but it can be worsened if you harass them.