Jedi Apprentice: The Deadly Hunter

The Deadly Hunter is the eleventh in a series of young reader novels that chronicle the adventures of Qui-Gon Jinn and Obi-Wan Kenobi prior to Star Wars Episode I: The Phantom Menace.

Publisher's summary
A mysterious bounty hunter has suddenly appeared. No one knows her name or her background. What is known, though, is her target: a friend of Qui-Gon's. The huntress ventures to Coruscant to track her prey. Obi-Wan and Qui-Gon fail to capture her, only to become her targets as well.