I hate my new step sister!?

Okay, so my mom after being divorced from my abusive father for 2 years found the man of her dreams or some ****. Be prepared, I'm gonna sound bitter. Well, I'm okay with the dude, he's nice and everything but he has the most fat,close minded daughter I have ever meant. My sister and I have tried to be healthy people for a long time, going to the gym everyday, eating fruits and veggies, mutual excersise, etc. Well, I believe in moderation... and I might have say a half a cup of chips a week or so. Well, I specifically ask for food for a reason, like say a certain vegatable or whatever. Well, today I found all of my chips that would last me around 6 months all gone downstairs with crumbs all over my playstation and a WHOLE box of strawberries gone. I knew who it was, that stepsister. That is basically kinda stupid but just wait. I am 13, and she is 14.. and I have always been sick by the smell of cigerettes... and she smokes while our parents are away in her room and it drifts around the house making me physically sick. She has gotten caught and got her phone and computer taken away, which is a minimal punishment since she has been caught 7 times before that! Also, she is in a constant search to find my faults, I don't have big boobs and she has C's (I have b's). I have yet to hit puberty to the full extent, so I have yet to completley devolope. Also, she is in a constant competition to see who is the best at everything, when I just roll my eyes and walk away she tries to make anything I do inferior. I'll say, hey mom I got all a's, and she'll say well i got more a pluses than you and start stupid **** about it. It's so extremley annoying and makes me very unhappy. I'm also kinda worried about her she is 5'2 and 170 lbs, and looks it, JS. How can I make her stop being such a dumb *****? I hint about **** to her but she doesn't get it. Also, how can I make her loose weight, she is really unhealthy.