I am surprized that Dante didn't mention the Panabakers.

Or Sammi Hanratty.

I'll go with Hayden Panetierre although he disagrees.

The original Dawson Casting did look pretty young, but not really little girlish. All of Katie Holmes, Michelle Williams and Meredith Monroe were passable as HS/college well into their 30s.

Overall the only woman who really looked girlish was Brooke Greenberg, may she never be forgotten. And her comrades. Nothing else comes close.