Maybe this is just me being a starry eyed optimist...but I think that IS something a woman can do. Maybe, inside at least one out of every ten sexists, there is someone who doesn't realize exactly what is going on. Ignorance and peer pressure and all that.
Maybe that person just needs a few examples to counteract what they're indoctrinated with. And if you can reach that one person just by being yourself...well, that's something at least.
But if the guy the woman tries to educate is not that one out of ten, or if he's the only one out of the gang of twenty he hangs with, she can end up in the hospital or worse.
ETA: I think there's a point at which social progress becomes like the economy: We all participate and we all can affect how it goes, but if it goes too badly off the rails, the best course for individuals becomes different from the best course for the whole group.
Example: In the current bad economy, it is better, safer and wiser for individuals to save money rather spend it. But all that saving depresses commerce and deepens the overall recession. But one cannot expect individuals to bankrupt themselves now to save everyone years from now.
Likewise, every person can influence the social norms and relationships around us, but if the social dynamic gets too far off kilter, people have to address their own safety before they worry about the direction of society. We can't ask women to put themselves in the way of a fist or a knife in the hope of enlightening a few strangers.
It's times like this when I think the world needs a little more socialism. In a lot of ways progressive socialist public/government programs seem hokey and forced, but during the 20th century, we saw them have good results that made it easier for individuals to reach out to others over time.