in a world where we're all so conditioned to believe that the only thing we should strive to be is the gabriella, we become so disillusioned when it is revealed that we're a sharpay. we fail to realize that supporting characters are individuals in their own right; sharpay has her own story and her own motivations. and who are we to demonize her for that?
what are you supposed to do when you grow up realizing that you're the mean girl that you're so conditioned to hate? you're to aspire to be everything that regina is not, yet you turned out plastic. but is that wrong?
these negatively portrayed women are still women; women with desires and passions that they hold true. these women exist in life. those mean "popular" girls, who seem to never truly have friends, are titled "popular" so no one feels bad about tearing them down.
these women exist and are more than a plot device to force the perfect protagonist into her perfect love interest's arms.