The Lord’s Persuasion of Lady Lydia by Raven McAllan
Dang when Lydia is out for blood it's up to Harry to settle her down:
‘Lydia, my love, you did promise to curb your bloodthirsty tendencies,’ Harry said with a laugh.
Lydia scowled. ‘Damn, so I did.’
I really liked this book, Lydia knew how to give Harry hell.