Hate being compared to my step-sister

I was raised by my mom and step-dad. I've known my step-dad for so long that he feels like he's my real father.His blood daughter, my step-sister, was raised by her mother, and our dad tried to be as much a part of her life as possible. My problem though isn't that he says she's better than me, but the other way.
She became a high school drop out, still hasn't gotten her GED after almost 10 years, she's always sponging money off dad and whoever her current boyfriend is, and by 19 she had already had two kids. And her personality doesn't make her come off as bright either, but instead kind of self-centered and mean.
I stayed in school, though performed pretty avarage, and went on to go to junior college. My personality, I guess, makes me come off as a straight and modest girl. So basically we are complete opposites, also in looks where honestly she has me beat in that category.

So I will over hear my step-dad talking about her and how disappointed he is and that he wishes she were more like me. And my mother who is much more harsh in comparaing us will call her a dumb slut. I don't like my step-sister at all, but with my parents reminding me of how proud they are that I'm not like her when I'm just trying to do my best, makes me feel pressured to not make any mistakes in life or to upset my parents in any way. I don't think I could screw up as bad as she has, but I still try to keep myself on my toes. Should I just relax? How can I?