Further on Aurra Sing, Lucas asked for a female bounty hunter, a sort of female Boba Fett, to be designed and thrown in as a cameo in Phantom Menace. The intention was she would play a role in the next Episode. It was sort of "showing the gun hanging on the wall in Act I because it is going to show-up in Act II" thing. So that was Aurra Sing and she appears in one shot during the pod race.
And yes, the character was built up in EU between Episode I & II. She was a failed Jedi padawan, I believe.
But, for whatever reason, Aurra didn't make Episode II and somehow I'm guessing it became the character Zam Wessel.