Pointing out the age here is a low effort way of saying that this person is giving advice about things she doesn't really have experience with.

Startup grind, big company ladder grind, marriage, university. Advice is given on all of these, but from what I can figure out from the website she only has minor experience with the startup part.

It can be an interesting read to see how inexperienced people view these things, but mostly this seems to touch upon something the author mentions in the post - self-confidence. She seems to have a ton of it to be able to dish out advice (to 80% of prospective startup founders) without having done any of it herself.

This. I think there are elements of fantasy of what it's like to work at a big corporate vs. working 'for' investors.

Also, I can't help thinking you'd learn a huge amount at YCombinator even if at the end of it you said, you know what, this isn't for me, you'd be doing it from a position of having actual experience that tells you that. She also mentions she'd prefer to work for a well founded early stage start up - I wonder where you can find those?