Antagonist.

Diane is the leader of a local motorcycle gang. Though she looks like a young woman most would meet at a bar or at a rock concert, it wouldn't take long for anyone to get a lesson in underestimating her. She is a tough cookie to say the least, and even though she is tough on her crew, she does care for them, in her own way. She doesn't seem to smile unless she's gotten something she wants, and it's usually at the cost of someone else's misery.

To me, she'd sound reminiscent of Jessica Alba.