Doxy for the Ton by Emily Royal

Her body was for sale, but not her heart. Until him.
Mimi La Fleur has survived heartbreak and destitution. The girl she once was is long gone and she never wants to be owned by a man again. She uses her body to earn a living, but her heart, and her pleasure, are not for sale. When she saves the life of a drunken duke, she’s reminded of a world long forgotten. He makes her an offer she can’t refuse—enough money to set her free, provided she agrees to be his mistress for six months.

Alexander Ffortescue, fifth Duke of Sawbridge, is notorious among the ton for indulging in all the vices London has to offer, but after he causes the death of his best friend in an accident, he’s disowned by all. When he’s set upon by brigands outside a tavern, he finds an unlikely saviour in a doxy, whose warm embrace and soft body give him much-needed comfort.
But Mimi is no ordinary doxy. Beneath the façade is a caring, compassionate woman who sees through Alexander’s rakish exterior to the lost soul within.