STAR SAPPHIRE

Star Sapphire was one of Green Lantern Hal Jordan's deadliest foes...and the one enemy that he dared not harm. Because beneath the facade of Star Sapphire was Carol Ferris, the love of Hal's life who unwittingly and unbeknownst to her was transformed into the villainess with the power to destroy through her mighty star sapphire gem.

Classification: Villain
Real Name: Carol Ferris
Age: 29
Group Affiliation: None known
First Appearance: "Doing Things The HARD. Way"
Favorite Drink: Miller Light bottle
Voiced by Olivia D'abo on the cartoon network
Powers: Light based powers similar to Green Lantern's, except fuchsia in color and channeled through a star sapphire gem on her forehead.

Notes: Carol Ferris may have been the love of Hal Jordan's life for a while, but now she's a major pain in the ass. She is pushy, rude, clumsy and totally inconsiderate...in short, someone who is handy to have around at closing time.

According to the "Green Lantern" comic books Carol was given the gem and costume by the Zamarons and became the Star Sapphire against her will. (They used some form of hypnosis to compel her to attack Green Lantern to prove he was weak and unworthy of her devotion.) When she failed to defeat Green Lantern in their first encounter, the Zamarons gave up on their attempt to make her their queen. (Since the Zamarons are immortal, they only choose a mortal as their queen to prevent a never-ending reign by one monarch.) However, Carol had subconsciously become addicted to the Star Sapphire powers. The Zamarons left the Star Sapphire gem on Earth when they departed, taking pity on her condition. Carol would periodically seek out the gem unconsciously, transforming into her villainous alter ego and temporarily assuaging her addiction. Her continual defeats at the hands of Green Lantern, coupled with some business reversals at Ferris Aircraft, the company she headed (and which employed Hal Jordan), eventually led to her breakdown. For all practical purposes, Carol is gone and there is only the Star Sapphire now.
You are quite correct that the "Justice League" cartoon has so far neglected to provide an origin. It may be she will turn out to be one of the other two women who have become the Star Sapphire in the comic books? One was an alien named named Dela Pharon from the world Xanador; and the other was an alien named Ramoni-Notra from the medieval world Pandina, who masqueraded on Earth as a Frenchwoman named Camille and Captain Comet's girlfriend (and real estate agent) Debbie Darnelle. (See "Green Lantern" issue #41 (Dec 1965) or "Secret Society of Super-Villains" issue #1 (May-June 1976) and "Justice League" issue #174 (Jan 1980).) BTW, in the origin story for Ramoni-Notra it states there were four women who were given the Star Sapphire at the time. Ramoni-Notra came to Earth to confront Carol Ferris, but at that time Carol was not using her gem. If we count Dela Pharon as one other, that still leaves one more woman unnamed.

Originally I thought:
Carol Ferris was Hal Jordan's boss and lover, before having a psychotic breakdown and developing a secondary personality. She was given a star sapphire gem by the Zamarons to make her their queen. Zamarons are the female counterparts to the Guardians. She has been primarily a Green Lantern villain. Star Sapphire makes an excellent Green Lantern villain since their powers are so alike, but she doesn't have the power to match the entire league. It's likely that if we see her return, she'll make it with other villains.

All of Star Sapphire's origins have basically been ignored. Hal Jordan's absence from both Superman and Justice League make it difficult to explain her origin in the cartoon. It seems as a side effect to the vast amount of super villains in Injustice for All, many origins of villains were simply ignored. Even when Star Sapphire made a second appearance in Fury her origin was still left out?