how do the celebs do it?

I'm 15 years old and my hair is almost to mid-back. My hair color is dark brown and aurburn on the bottom due to previous highlighting. I really want to bleach my hair full blonde, somewhat like Jessica Simpson I guess you can say? Although everyone says bleach is unhealthy. If this is so how come Paris Hilton,Nicki Hilton,Pamela Anderson, and so on get beautiful results and don't seem to have brittle hair at all? Is there a way to bleach your hair and still keep it looking healthy like that? Should I go through all this trouble or should I just get a wig, or do they even look natural?

Thanks

Yes Extensions is the way to go, my hair changes almost as often as them, and trust me my natural hair is CRAP, fine thin and damaged beyond repair:P Shure Sunsilk an Kpack Reconsructer works, but there is some extend on what Kerastase and flatironing can fix. So now i am growing my hair out, and for the moment is covered by extensions hiding the damaged...Just let it rest!^^

But you could do it, but you have to cut it, if you get a layered bob to an above shoulderlengt and then add some extensions i think the outcome should be great, almost all celebs , Jessica and Ashlee Simpson, Chrisina Aguilera have shoulderlengtish hair O.o