Name: Femme Mysterieuse
Alter Ego: Joelle
Other Names: Mysterious Woman
First Appearance: Gambit (vol. 5) #1 (Oct. 2012): "Once a Thief... Part One"
First Appearance (Additional Details): (named) Gambit (vol. 5) #4 (Dec. 2012): "She's the End of the World"
Super? (Has Super Powers/Special Abilities/Technology): Yes
Number of Appearances: 9
Family/Relative: Olivia (daughter)
Note: granted immortality; sought way to end life
Joelle was granted immortality by a yet-unidentified individual. Joelle loved her daughter very much, but because she was immortal, she watched her daughter grow old and eventually die. Joelle wanted to end her life so that she could rejoin her daughter in the afterlife. She sought out a way to end her own life, but found this was not an easy quest.
Before Gambit learned Joelle's name, he referred to her as "Femme Mysterieuse" (which means "Mysterious Woman" in French) because she was very mysterious and he did not know anything about her. "Femme Mysterieuse" is not an actual codename that she used herself.
Suggested links for further research about this character and the character's religious affiliation: