How should Penny Pingleton be portrayed in Hairspray?

I have a callback for Penny Pingleton in my community theater's production of Hairspray. I know she is the slightly ditsy best friend of Tracy Turnblad. She's devoted to her friends and feels smothered by her religious mother and her ridiculous rules. But I really want to ace this callback so does anyone have any ideas of how I should evoke Penny?