I've seen that in other women. When they can get what they want at an early age by having a shorter skirt than the other girls, why develope anything else? I personally believe she's that dumb.
And I agree with Chief. I've had a few girlfriends that were so gorgeous I felt lucky to fuck them. After a couple months of that, it became more obvious that they were dumb, a slacker, a bitch...whatever her deal was....and great pussy just wasn't enough.