The Duke and the Spitfire by Jessie Clever

Lady Johanna Darby has loved Benedict Carver since they were young, but he’s never seen her as more than his best friend’s little sister. When Benedict marries another and emigrates to America, she knows she will never love another. But with her sisters all wed, Johanna resigns herself to finding a match to finally leave her family home and give her brother his much-deserved freedom to find his own wife.

Until Benedict unexpectedly returns, newly titled and widowed.
Benedict Carver never doubted his place as the second son of a duke, mostly because his father would never let him forget it. Denied the station he desired at his family’s beloved Raeford Court, Benedict is sent to America with the bride his father chose for him. But when his brother dies in a tragic accident, Benedict finds himself with the title and an estate on the brink of collapse thanks to his brother’s gambling debts and neglect. Having sworn never to remarry, Benedict must now select a bride with a hefty fortune if he is to save his beloved Raeford Court.

Even if that bride is his best friend’s little sister.