How are things deemed worthy of wikipedia? Why do they have the right to delete pages?

I have a friend who is a popular folk musician who became a big hit on the internet. She is a comical genius and tours with her funny ukulele songs. She has been invited to many cons across the USA. She's beloved especially in the greater atlanta area. However, when I created her a wikipedia page wikipedia nominated it for "speedy deletion." If you read all of their "this is why you create a page" and "speed deletion" and "why it's deleted" and "how to dispute" none of it makes ANY sense. How do you know if something is "worthy" of wikipedia? If there's not "editor in chief" why does anyone have the right to delete pages? Wikipedia is just a crappy non-scholarly version of pop culture and general information. It doesn't have any sort of real relevance, but I thought it would be nice to add her a page since she didn't have one on there. And it was immediately deleted because it was deemed "unworthy" by three people who are just users on wikipedia. I don't understand why or how this is the case. Can anyone explain it to me?