Film School Rejects does a really great interview with Diablo Cody on the release of her directorial debut Paradise. (Side note- Many of the interviews she has done for the release of this film have been stellar.) She is one the best when talking about women's issues in Hollywood. (Make sure to read what she says about Gravity.)
Here's her answer when asked how she defines a strong female character.
I’m perhaps alone amongst my colleagues because I like talking about women’s issues in film, and feminism. I think a lot of women don’t like to do that. It’s usually, “Can we please turn the conversation back to my work?” For me, it’s an important part of who I am. I feel like so much of the reaction to my work and to me is connected to the fact that I’m a woman, so I can’t avoid that conversation. A part of my career is that I am a woman and I’ve committed myself to writing roles for women. I cannot separate myself from that and say, “Oh, can we please just talk about my work?” That is my work.
She is committed to writing roles for women. I love her.