Have y’all read The Oatmeal’s treatise on how Twilight works? He makes the same points you did about Bella, but with pictures.
I think Bella is easier for readers to slip into than Ana is.
Every teenage girl is clumsy, awkward, and shy sometimes (unless she’s superhumanly well-adjusted), but most teenage girls don’t have anxiety so crippling that they’re afraid of other people. As someone who’s been a whiny teenager with anxiety issues, I can relate to Ana—but that doesn’t mean I like her or want to take on the role that she has in Fifty Shades of Grey.
Many of the women who like Fifty Shades aren’t teenagers, either. They’re adults. Explain that one to me.
I personally believe that Ana’s love for old literature was put in place to make both her and E.L. seem ~intelligent and special~, as well as give Ana some kind of character trait beyond unparalleled shallowness. That doesn’t mean it worked.
It’s important to keep in mind that Twilight started out as a self-insert-type vanity novel and that Fifty Shades of Grey began as fanfiction. Neither Stephenie Meyer nor E.L. James had much of an audience in mind while they were writing their debut novels. This is particularly clear in 50 Shades, where E.L. constantly alternates between using obscure, technical words (albeit incorrectly) and between reminding her audience of things that are supremely obvious.