vacaloca, i read your link.. all those things are true but i think they also manage to miss the point somehow... or at least gloss over the numerous references to Bella's strength, her courage, her independence etc. she takes care of her mum, her dad, she is actually rather loyal to her friends (ok so she only has a few, perhaps only one, but lots of people don't have lots of friends).
moreover, teenage love is obsessive, exclusive, claustrophic and completely bonkers- god i remember being madly "in love" with a guy in my high school i had never even spoken to, i would have done anything for him! i once spent an afternoon combing through the entire telephone book (whcih was split by suburb and then by alphabetical order, rather than the other way round) so i could find his number, memorise it and... that's it, i never even called!
i think teenage girls see themselves reflected in Bella, rather than trying to emulate her, if that makes sense?