How to deal with a stubborn sister?

@munach (49)
May 3, 2010 3:00am CST
I have a younger sister( a teenager) who is so spoiled that even my parents can't do anything about her stubborness. She loves to go out every night and when it comes to doing household chores, she's as lazy as a cat.I don't know how to reprimand her,she doesn't even listen to what my parent's advice.Her stubborness started when she got dumped by her first boyfriend.I'm just concerned about her because before she was an obedient daughter and she had good grades at school.It's a sad thing if she continues to be that stubborn, her future will be wasted.HELP!