Once a member of Philadelphia's crime-for-hire organization, Danielle Ryrie has vowed to make some good come of her life. In 1903, she moves to New York City and finds legitimate work in a family-run restaurant, and her employers accept her as their own. When the extortion gang known as the Black Hand targets her new family, Danielle calls on her destructive training to protect both her employers and the business. Soon the opportunity arises to fell the city's criminal hierarchy, and she allows herself to be drawn back into her former lifestyle. At the height of her war against the Black Hand, Danielle realizes her own corruption when she kills a plainclothes cop. (here's your hook) Desperate to regulate her murderous tendencies, she hires the Black Hand's assassin under these terms: if she ever kills again, he must kill her.
arises to fell the city's criminal hierarchy?
regulate her murderous tendencies?
Those are all candidates for Clunk and Graceless the Writing Hall of Ill-Repute.
Start with last sentence because the crux of your story is this woman trying to straighten out her life.