I'm still envious of my pretty cousin
Why would you be envious of her?
Because she's prettier than I am.
It's understandable to be envious of someone's look. You shouldn't get yourself down over it though because it can affect your self esteem.
Guys only care about looks.
It makes sense that you want to be pretty. That is what is pushed on us by society but don't you also want to just be yourself and be happy?