Aurra Sing is a Sith Apprentice in Training and will be a Sith Lord in Ep. III

It makes sense. The cameo in Ep. I. The Red lightsaber she carries. The fact she was on Tatoonie (either on a mission for her master or as training to help find the missing Queen). The drawings of her in the art of Ep. I show that she was indeed supposed to be a Sith Lord originally. In Ep. I, she either answers to Darth Maul or Darth Sidious and one of them is training her. Lucas is not going to waste such a popular character with the fans (see "Boba Fett", his cameo on the Christmas Special & the one inserted in SW: ANH - SE). I just hope that she is super sexy and seductive in a "Dark Side" sort of way. That would give Ep. III some much needed HEART & SOUL and it would fit nicely into the ANAKIN becoming VADER feel. Maybe her new name could be Darth Natrix "get it!"