Six Angry Girls by Adrienne Kisner
Raina Petree is crushing her senior year, until her boyfriend dumps her, the drama club (basically) dumps her, the college of her dreams slips away, and her arch-nemesis triumphs. Things aren't much better for Millie Goodwin. Her father treats her like a servant, and the all-boy Mock Trial team votes her out, even after she spent the last three years helping to build its success. But then - an advice columnist unexpectedly helps Raina find new purpose in a pair of knitting needles and a politically active local yarn store. This leads to an unlikely meeting in the girls bathroom, where Raina inspires Millie to start a rival team. The two join together and recruit four other angry girls to not only take on Mock Trial, but to smash the patriarchy in the process.