Jimaine is daughter to Margali Szardos, a powerful sorcerer who raised Kurt Wagner (Nightcrawler) when her true mother abandoned him. Both of them and Stephan, her elder brother, grew up together working in the circus, but eventually, Stephan turned evil and Kurt had to kill him in a duel and left Jimaine, who was in love with him. Jimaine then also left the circus and became air hostess, being herself a powerful sorcerer, although not of the same type than her mother, for Margali has to spent big privations every time she increases her power. She adopted the name of Amanda Sefton and changed her look, so when she met Kurt again, he didn't recognize her.
They spent some time as a couple before he discovered her true identity, when Margali made him believe that he has gone to Hell (a hell like the Dante's description), as vengeance for his son death, and the X-Men had to rescue him. Before that, she was once captured by Arcade, as well as Moira, Illyana and Stevie Hunter, to force the X-Men to come into MurderWorld. She didn't use her powers then, maybe to keep her secret identity unrevealed.
She was not very interested in becoming a superhero, so she spent her time flying and used to appear when the X-Men needed her, but became involved into the Shadow King affair, being controlled by him. At the end of all that, she still didn't became a full-time member of any team, but her appearances in Excalibur were more frequent.
Her relationship with Kurt has had his high and lows, but lately it seems to work O.K.