The Girl with the Louding Voice by Abi Dare.
Adunni is a fourteen-year-old Nigerian girl who knows what she wants: an education. This, her mother has told her, is the only way to get a “louding voice”—the ability to speak for herself and decide her own future. But instead, Adunni's father sells her to be the third wife of a local man who is eager for her to bear him a son and heir.
When Adunni runs away to the city, hoping to make a better life, she finds that the only other option before her is servitude to a wealthy family. As a yielding daughter, a subservient wife, and a powerless slave, Adunni is told, by words and deeds, that she is nothing.
But while misfortunes might muffle her voice for a time, they cannot mute it. And when she realizes that she must stand up not only for herself, but for other girls, for the ones who came before her and were lost, and for the next girls, who will inevitably follow; she finds the resolve to speak, however she can—in a whisper, in song, in broken English—until she is heard.