I resent my younger sister because she is better than me
I understand what you are going through. Is there a reason you feel your younger sister is better than you?
She always looks pretty and boys like her better. I've been compared to her a lot although she is younger than me.
It can be hard to not compare ourselves to others, but it's not a healthy thing to do, especially when it's to our siblings. You should try to have more confidence in yourself, as you surely have many wonderful qualities.
She's pretty and she gets away with everything. Boys like her because of her looks.
I can see how you would be frustrated by this. You shouldn't be in competition with your siblings. You have your own qualities to be proud of and shouldn't put yourself down.