She was made to be an evil version of Chun-Li, she has increased speed and cyborg-based moves. Its speculated that she is a cyborg created by M. Bison to match Chun-Li. Due to the fact that she didn't appear in any other Marvel VS Capcom game, she probably was destroyed by Chun-Li or someone else.
A character similar is Shadow, who is Charlie Nash after being abducted by M. Bison. In her ending, an evil version of Jin Saotome also appears, later called Shadow Jin. In this same ending, its shown that both Shadow and Shadow Lady have defected from Shadowloo, as they were trying to save Jin from M. Bison, but arrived late.