It's the name of a tvtropes article.
She likes sports, beer, cars, swearing, fighting and sex. She is crude, rude, often hygienically challenged and cheerfully ignorant and aggressive. If you are a guy, she'll probably challenge you to a fight or a drinking competition, win both and then take an aggressive lead in anything sexual that happens, before kicking you out the front door the following morning or teasing you mercilessly if she lets you stay some more.
In short, she is a young woman with the personality of a frat boy. She is the Lad-ette.
While I don't do the drinking or sex stuff....usually....i'm foul mouthed, heavily into sports, and rough around the edges.