My sister listens to that music for almost purley for rebelion. She has Swastikas painted on her wall because she says they look cool, in reality she just wants to piss people off. She is not in any way a Post-Nazi she just likes to shock people.
Thank your lucky stars she's chosen to rebel through decorating and music. Would you rather she do it through having an eating disorder or something? Teenage angst is usually about control - you pick something in your life you do have control over and focus on that, then you don't have to worry about all the stuff you don't feel you can control. There are plenty worse outlets for that feeling than music.
She really dosent care for other peoples feelings or opinions.
Have you considered the same might be said of you if you try to impose your taste on her without stopping to consider why she likes what she does?
Also, have you considered she possibly thinks exactly the same of you for your love of classical music as you do of her? 'My brother's a classical music type, he only does it to try to prove he's different, he tries to force it on me because it makes him feel clever and important'. (I hope you take that in the spirit it's intended, I'm not trying to insult you, just to point out that your sister may look at things a little differently!)
If you want to show her some of the things you love about classical music without starting rows, you have to meet her half way. Choose music she'll know for starters. If she likes her rock bands, why don't you buy her a recording of the Queen symphony for her next birthday? She'll probably already know the tunes and then it's just a question of presentation. Or maybe her favourite film's score? An awful lot of people now only listen to an orchestra for an extended period in cinemas, when they're being distracted so don't notice they're sitting listening to classical music.
Also bear in mind that unless they're at a concert or show, most people won't just sit and listen to a whole classical CD and call it entertainment. Put it on in the background while you're doing something else around the house. Music tends to permeate - just as you can hear your sister's music around the house. I'm not saying put it on loudly and compete - but I initially learned about classical music because my grandmother in particular listened to it a lot and it was always just there in the background. And I suppose I associate it with her and all the things I loved about her.
It seems to me that Clasical music has a huge bias against it. Why?
Many reasons... one main one being the attitudes of a lot of people involved with it which have a nasty tendency towards snobbery. This can make it seem both difficult and elitist to people outside classical circles.
Classical music has an image of being older people's style - and it is, mostly because it takes most people a certain amount of maturity to develop the interest and attention span.
It's expensive - not just if you're learning an instrument. CDs at £30 or opera tickets at £100+ a time put the cream of classical performers beyond the reach of most people, especially most families, certainly on a regular basis. I've got lucky this season and will be going to hear Placido Domingo sing at Covent Garden - but the weekend in London and the ticket price will cost me around £200. It's certainly not something my parents could have afforded for me when I was growing up, and only something I can afford for myself now I'm independant and earning reasonable money. Contrast this with, say, Robbie Williams - a handful of CDs at £15 or less, concert tickets under £50. That's an investment most families can afford to support their child in if said child likes Robbie Williams.
It's badly marketed and publicised to the mass market. Some classical performers are starting to try to appeal more to the masses, but most people don't know where to find out about their local concert circuit. It's also notable that those performers who do choose to play to the masses - Russell Watson, for instance - are sneered at by the rest of the classical music world, who do their best to ostracise them. If you asked most people to name famous current classical music stars, you'd probably just about get Nigel Kennedy, the Three Tenors, Lesley Garrett or Russell Watson named. Even serious classical music people can usually name more famous rock bands than that.
All of the above meaning - unless you're born into a family that brings you up with classical music and can afford to support any growing interest in it on your part, you probably won't be offered any opportunity to get involved with it until you're old enough and rich enough to do it for yourself, and even then you'll probably need something outside yourself to get you motivated to do so - acquiring a friend with an interest in classical music or falling in love with a film score or something.