Elizabeth Koopa was Bowser's real first daughter, but Bowser never told anything about her to the other Koopalings. Elizabeth is also daughter of Mrs. Koopval, which was Bowser's first wife. (So Clawdia is the Koopaling's Stepmother!!!)
As you can see in the picture, Elizabeth has pure black hair and a black bow with white polka dots, a black shell with yellow-surrounded spikes. She has a wand with a black top.