The Unstoppable Letty Pegg by Iszi Lawrence

Lettice Pegg's father is a working-class policeman and her mother is a middle-class suffragette. Stuck between them (and her terrifying grandma) as they argue, Lettice mostly cares about trying to fit in at school and convincing her parents to let her have roller skates and go to the music hall. But, when Lettice sees her mother brutally thrown to the ground by a policeman while on a protest march, her life changes forever.

Not all of the women on the march are vulnerable to attack. Some of them have a secret weapon: Jiu Jitsu. As the suffragettes welcome Lettice to the fight back, things at home go from bad to worse.

Can Lettice bring her family back together and keep her new friends?