Claudine is the leader of the Resistance. She works as a doctor by day and guides the Resistance by night. As such she is responsible for recruiting Battle Mages, Wild Hunters, and Mechanics, allowing the Demon to help fight the Black Wings, instructing her savior from the Black Wings, Xenon, and in general missions the Resistance coordinates.
Claudine was friends with Xenon when the two were just kids, but Xenon was kidnapped by the Black Wings to be tested on. Claudine joined the Resistance when she grew older, and while breaking into Gelimer's Lab, she was captured. Xenon found Claudine and was confused; His memories started coming back to him, and he set Claudine free.
Appearently she is a Thief job instructor, as revealed in dialog with Elex. Although there is no official job in the Resistance that plays in with Thief.