You give her mental powers

If Megan is going to go up against Hypergirl, she's going to need some serious powers. It's time for the debut of... The Mind Mistress!

First, some serious telekinesis. You make a quick wish, then watch as Megan rises into the air, using the power of her mind to effortlessly propel herself aloft. She then looks out a window at Gerald, the fattest freshman ever, walking towards the school. With a cruel giggle Megan lifts him into the air and strands him in a tall tree.

Next, you give Megan a bit of ESP. Not enough to see the far future, just enough so that she can see five seconds ahead. That should make sure she can dodge any cars that Hypergirl throws at her.

Finally, you give her the ability to read minds and control people. She can't reprogram people's personality, but she can make them do things against their wills.

The only mental power you don't give her is increased intelligence. Megan was never the brightest girl, and it just wouldn't feel like her anymore if she had brains in addition to power and beauty.

The only things she needs now are some tweaks to her costume to fit these powers. You leave the short skirt and tight top, they look too good to change. You just modify the colors so that they're black with gold trim. The school logo on her top changes to a gold "MM", though it's hard to read stretched out across her enormous breasts.

To top it off, you give her a little black domino mask. It isn't enough to truly hide her identity, especially not with a body like that. So you wish that she can also use her mental powers to cloud people's ability to recognize her.

At that point you forget that the Mind Mistress is really Megan the cheerleader, meaning that you also forget that you have any power over her. All you know is that a gorgeous blond supervillainess is floating above you with an evil grin on her face.

"Well, well, what do I have here?" she asks herself as you fall to the floor, pinned down by her powers.