Lucy Lane: All you need is a couple of streaks and your ears pierced. I could do it for you, it's easy. You just get a needle, heat it up, dab it with some alcohol, and zap! The guys go crazy.
Linda Lee: My ears what?
Lucy Lane: Pierced. Like and you know, I take a needle, and then I heat it up, dab it with some alcohol and, zap, all the guys go crazy.
Linda Lee: Because I have holes in my ears?
Lucy Lane: What, are you putting me on? Sometimes I can't figure you out, Linda.
Selena: I'm considering nothing less than world domination.
Lucy Lane: Look at that dingleberry.
Linda Lee: What's a dingleberry?
Nigel: Oh, terrific. The old dangling-in-a-cage routine. Pathetic, Selena.
Answer: It's never explained, she could have changed at super speed. In Superman II, when confronted by the super criminals at the Fortress of Solitude, Superman did a disappearing and reappearing act. So did the criminals. It might be a similar thing.