Because being young does not mean you have to be immature, and sexism should have nothing do with either immaturity and youth.

And indeed - by declaring yourself mature enough to handle a startup at a young age, you're also declaring yourself mature enough to act like a human being. Young people in prominent settings shouldn't get a free pass - if you want to be in the "big leagues", you've got to act like you belong there.

OK, but millionaire CEOs and invented the Old Boys Club, so what does success in business have to do with egalitarian respectful behavior toward all?

That's an unsubstantiated claim. I don't think it's true. From what I've heard about the YC interview and decision-making process I think they place a high value on maturity. The ones I've met have fun but don't have rockstar attitudes.

Also the awkwardness she's talking about doesn't come only from having a big ego. It's from constantly saying a single asinine statement. The person saying it often doesn't mean for it to have the effect it does.

"Rockstar" is a meaningless word. Real rock stars, like famous musicians, work their butts off with large teams, and then celebrate, sometimes too hard.

Her bio says where she works, and it's not a startup, let alone a YC startup.