Black Sails to Sunward - Sheila Jenné - Bog

In a world of frock coats, solar sails, and rigid class boundaries, Lucy joins the Martian Imperial Navy as a midshipman. Mars and Earth are at war, and Lucy hopes for quick promotion. But when she arrives aboard ship, she finds her childhood ex-friend, Moira, already there. Class differences got in the way of their budding romance five years ago, and both of them are nursing grudges.
Those same class differences are threatening the ship, as the enlisted spacers threaten a mutiny and Lucy is forced to support the abusive officers. When Moira becomes a pirate, taking Lucy captive, the tables are turned. Lucy now has to rely on her enemy for her life.
Her oath as an officer forbids her from helping the pirates, but it's becoming obvious that the Martian Empire doesn't deserve her loyalty. If she throws in her lot with the pirates, her family is doomed to poverty, but it could give her a chance to reconcile with Moira and claim the love she rejected so long ago.