The Be All and End All — Patti Larsen

Susan's parents have refused to let her out of their sight since her disappearance, making it impossible for her to return to the city. Without Tucker at her side, her cat friend trapped and unable to reach her. She has to sneak away, returning to discover the city she loves is slowly dying! And nothing she does seems to be able to help. When the truth about the power of the sorceress and her people comes to light, and Tucker's destiny is revealed from an unexpected place, it's up to Susan and her faithful friend to break the final spell before their old enemy can steal the last of the city's magic and destroy everything.