I'm not sure that's a boy-girl thing. I've had group projects in college where similar things happened, and it was just easier to do the work than to argue with the other people. (The one time I didn't, one member of my 3-member team dropped the class, and the other switched to pass/fail, the night before the project was due.) About an even mix of boys and girls.
I never came up with a good solution for the artificial situations you're forced into by teachers. You can do more than your share of the work, you can be happy with a bad grade, or you can luck out and get good teammates.
Girls do tend to be socialized more toward the "do more than your share" than the "be happy with a bad grade," though.
