If you're going to protect your family and keep your enemies from figuring out who you are, you need a secret identity. Something so elaborate that they would never know you were a hero.
And then it comes to you. Right now, you're a fully-grown woman in a skintight spandex suit. But what if you weren't? What if you were, say, younger? Your body is capable of stretching in all sorts of ways. What if you could manipulate it so that you looked like a completely different person?
Just then, you spot something in the corner of the room. A small, dusty book. You pick it up and read the cover: "How to Handle the Middle School Transition for Boys and Girls."
That gives you some inspiration. You start flipping through the pages until you find a section entitled: "Changes in The Physical Appearance of Girls." The author explains that middle school girls are expected to undergo many major changes to their bodies. Their breasts start to grow in, they start getting noticeable hair around their crotches and on their legs, they begin to menstruate, and they get taller.
With this as a guide, you shrink yourself down until your adult height is halved, and then work on making every part of your body, from your fingers to your toenails, smaller, but not too small. You make a mental note to make sure your body "grows" a little every month so it looks like you're developing as a middle schooler should. You even make sure to put some "hair" on your crotch and on both of your legs. No one would think otherwise if you didn't shave those areas yet.
Everything is almost ready. The last thing you need...is a new face.
Fortunately, the book has a section in the middle, full of pictures of boys and girls of all sizes and shapes. You run your finger down until you find one that most closely resembles what you look like as an adult. Huh. You actually look really cute. Maybe you'll snag a few boyfriends along the way.
By the time you're finished, you look like someone straight out of a tween fantasy novel, with straight brunette hair that goes down your back and a face that would have looked passable on an American Girl doll. Maybe you should try to do something with your hair, you wonder.
But then reality snaps back. You need clothes, makeup, accessories, and a school to go to. And you know exactly who to ask for the latter.