Bitter Seed by Meg Hutchinson
Having suffered much cruelty at the hands of her father, Isabel Kenton is shocked to hear after his death that he was not her real father. She inherits their house while her twin brother Mark is left the family steel works. When World War I breaks out, Mark joins the RAF, and the management of the business is left in Isabel s hands, which is not welcomed by the town s industrialists. She makes many enemies and has to struggle to keep her business alive. After much unhappiness, she finally finds love with the manager of a local foundry as well as the identity of her real father.