Intriguing & Evocative:
* The Shadow's Daughter
* Whispers in the Dark
* Blood Rose
* Silent Blade
* The Girl Who Hunts the Moon
* The Assassin's Requiem
* The Price of Silence
Direct & Action-Oriented:
* Runaway Killer
* Angel of Death
* The Killer's Apprentice
* Vengeance Unleashed
* The Last Bullet
* No Escape
Character-Focused:
* Lily's Revenge
* Ava's Shadow
* The Girl with the Gun
* The Serpent's Embrace
Adding a Twist:
* The Assassin's Daughter
* The Family That Hunted Her
* The Price of Freedom
* The Girl Who Couldn't Die
Ultimately, the best title will depend on the specific story you're telling. Consider what kind of mood you want to set, and what aspects of the story you want to highlight.
Bonus Tip: Think about the genre you are writing in. A title that works for a thriller might not be as effective for a fantasy novel.