How come she has a better body then me?! please help?

She has a higher metabolism, she can eat what she wants and it wont get her fat (even though in 30 years its probably going to hit her like a bullet). You're actually a little bit skinnier then or the same in height to mass, and you have a very healthy bmi. To be honest, its just because you're a teenage girl, in your mind you probably think that she looks better then you, but I bet your friend secretly longs for your body too.