I think you're being a bit unfair, here, and not to mention a little cruel. If you read the comments to her videos in INxJs, it's clear that she's 'not for us', but I don't she how she can be labelled 'dumb' just because of her carefree approach to life and ditzy aspect.
According to the Official MBTI stats, ESTPs are pretty average when it comes to educational attainment up until the postgraduate qualifications, but we can see how a lot of them just would not be interested in going deep into education simply based upon the preferences of the personality. What's the point in pursuing a doctorate or masters when all you want to do is experience life? In any case, attainment isn't intelligence.
She seems fine to me, but she is 'living in a different world', and that lack of mutual understanding might put us off.