Asteria, Asterism's alter-ego

An then I was ...!

So, why does she hide her glory from her parents?

Because she's a spy. And since it's Equestria she can get by with Clark Kenting...

Make sure she wears glasses. That'll fool them.

EXACTLY.

In other news, I like the old-school cutie mark

I guess some color schemes are just more common than others. Can you imagine trying to stand out if you were a grey unicorn stallion?