As Twilight demonstrates, not everything girls like is good art — or, for that matter, good feminism. Still, the Twilight backlash should matter to feminists, even if the series makes them shudder. If we admit that girls are powerful consumers, then we admit that they have the ability to shape the culture. Once we do that, we might actually start listening to them. And I suspect a lot of contemporary girls have more to talk about than Edward Cullen.
In a weird way, Twilight is like a good deal of anime: to the outsiders / uninitiated, its appeal is incomprehensible. You hadda be there, and a good deal of how you get there in the first place with Twilight is by being the target audience.
I keep wondering about the dichotomy you get between a creator and the target audience. Most of the genre writers (to say nothing of the non-genre writers) I know are holding their nose at the whole of Twilight, but it's impossible to ignore that the books command an audience. Yes, an audience that may soon outgrow the material in a couple of years, but an audience nonetheless — and when you fall out of touch with what the potential audience is, you do yourself a disservice. That explains why something like The Catcher in the Rye falls so flat with today's kids: the youth it was written for probably ceased to exist thirty years ago or more.