The Sister Of Tony Stark

Everybody thinks that when you're related to the rich and famous, you're rich and famous. They're wrong.
My name is Flinn Stark.
My brother is Tony Stark.
And Tony has all but forgotten about me, even though I live in Stark Tower.
I hide away in my room, an agorophobe if you will.
And I'm happy to be isolated and alone from all the people.
Because alone is what I have, alone protects me.
So while in isolation I discover my potential.
I can control the elements.
So when Loki attacks New York, I come out of hiding and tell the Avengers about myself.