Why be like her?

Be like your sister,be like your sister! Thats what my entire family coaches. But why?!I have like asked that Q so many times!Beauase she is an angel in your parents eyes, they answer.
And they are right man!She does every thing they tell her to... infront of them,if I show her how she really behaves they would both probably have a heart attack, NOT joking.My exam marks are TERRIBLE!So last night when they saw my papers,they completel ignored me,infact, the ony words we exchanged today were a hello and a good bye.
Not only that but she takes my stuff and proclaim them hers.Like my prized wallet my best friend gave me.She also keeps going on and on and on about HER good marks which my situation worse. I have swore to my self that I'll do better next term,but will they ignore me until then? Since young I have been spoilt,I don't know if I can take this much longer.
I have not told my friends what has happened, will they shun me if I do?! I have been keeping to myself lately at home,it is making my fave aunt moody,the aunt I talk about in the first post. Write later,
Hopelessteen