The Bride Who Got Lucky by Janna MacGregor

He would do anything to protect her. Even marry her…
The son of a cold-hearted duke, Nicholas St. Mauer isn’t one to involve himself in society…or open his own heart to anyone. But driven by honor, the reclusive Earl of Somerton feels obliged to keep a watchful eye on Lady Emma Cavensham. She possesses a penchant for passions unbecoming a woman that finds Nick in constant peril of losing his well-structured solitude. She even dared kiss Nick once―an utterly unladylike, and delightful, lapse…

Emma can’t deny the appeal of the earl’s attention, and occasional affection, but she has no need for a man. There are worse fates than spinsterhood, as Emma knows too well. She still mourns the loss of her dear friend Lena, and is determined to prove Lena’s husband responsible for her death before he lures another innocent woman into a brutal marriage. But as Emma pursues her prey, a compromising moment upends all her plans. Now, with gossip swirling and her reputation in tatters, Nick may be the only man brave enough to join in Emma’s cause. . .and fight for her heart.