Showing Bad Elements: Crystal Dragon by Lynn Mullican

Crystal Bouchard awakens imprisoned in an underground cell with no recollection of how she got there and with no memory of her prior existence. Held against her will, her captors threaten to kill her son unless she fights to the death in the underground fighting circuit. Nicknamed "The Dragon," she spends the next several years among werewolves and vampires.

During the course of searching for her son, she slowly begins to recollect her prior existence before her imprisonment, pushing her deeper within the fighting circuit.