You don't have to look like them to be beautiful ! And most of the time these girls are unhealthy but if you really want to be like her try to stay the way you are now, don't afraid to be yourself
Those images you posted are very misleading - and often times the subject is either sucking in/flexing or simply using the lighting to achieve a certain look.
Delete them off your phone! >: (
J/k :P
But do your best to pick apart images you see, find the truth under them. Being skinny/"attractive"/etc.. is not confident. Confidence comes when you are familiar with the territory. Are you familiar with your territory? (Your body/mind)
We have this internal compass that will help guide us to inner peace. It's that good feeling you get when you're doing "that thing that you do". Envy, jealousy, these will make you feel unfulfilled when you are like an apple seed. You have everything you need for self success inside you already. Look for that, get familiar with that, and see where it takes you.