Ganurath:
I was thinking PL 10 to start off, since you want your character to be new to the super scene. Strong, but not so world-shaking that the Organization of Abstract Noun will break out the big guns to contain her when she flips. As for edition... I'm afraid I'm only familiar with 3e.
Also, since you requested an Adult game, keep in mind that I'll be sitting on a ten foot pole where the site's Adult Policies are concerned when you're deciding how old your Pintsized Powerhouse is.
I'm fine with PL 10, but would you consider giving us more power points per level? Hell, we could do PL 8 so long as there're more PP/PL. And 3e is great. The fact there's an SRD makes everyone's life easier. That said, I have to remember how to recreate the Density power from 2nd. ^_^
All characters will be over the age of 18, don't worry.