Despite being one of DC's most recognizable heroes, Wonder Woman's origin story has never been as set in stone as Superman or Batman's. Originally Diana of Themyscira was molded out of clay by her mother Hippolyta, but her origin has been revised and expanded a number of times until the modern era. Her most recent origin story, and the one which the movie mostly follows, is that she was the daughter of Zeus and Hippolyta. Though Wonder Woman's many origins can be complicated, they are nothing compared to the tangled web of backstories and retcons created for Wonder Woman's first sidekick, Donna Troy.
The confusing nature of Donna Troy starts before her first appearance. When the Teen Titans first premiered in 1965 the team consisted of sidekicks Robin, Speedy, Aqualad, Kid Flash, and Wonder Girl. All of these characters had a history outside of the Teen Titans and would have been familiar to comic readers at the time. All of them except for Wonder Girl. Unlike many other DC heroes, Wonder Woman did not have a sidekick. There was a Wonder Girl within the pages of Wonder Woman, but only in non-cannon stories where Wonder Girl is a teenage Wonder Woman from the past. The Teen Titan's creators mistook this past version of Diana for an entirely separate character and added her to the Teen Titans.
Soon after the Teen Titan's solo series began, the creative team behind the book realized their mistake and gave Donna Troy her first origin story in 1969. Originally, Donna Troy was a young girl rescued from a burning building by Wonder Woman who took Donna back to Paradise Island. Donna was then raised by Queen Hippolyta, which led to Donna becoming Diana's younger sister. This origin would receive a small expansion during Donna's time with the New Teen Titans where it was revealed that her biological parents were alive and that she had been kidnapped by human traffickers at a young age. Just four years later, this origin would be revised as a result of Crisis on Infinite Earths. Due to timeline issues, it no longer made sense for Wonder Woman to have rescued Donna, so instead, it was the Greek Titan Rhea who rescued Donna, gave her powers, and brought her to Paradise Island. During this period, Donna changed her costume and adopted the codename Troia. This revised origin would only last until the nineties.
After years of being on the New Teen Titans, Donna's character became more focussed on her home life. She had married a much older professor of hers named Terry. Despite the unfortunate nature of their relationship, the first major complication arrived when Donna became pregnant. A new team of heroes called the Team Titans arrived with the goal to kill Donna because her son would end up as a dictator called Lord Chaos. The storyline ended with Donna losing her powers and her marriage. All of this led to a third new origin story. Donna was now created by a sorceress to be a duplicate of Wonder Woman but was abducted by a supervillain named Dark Angel. Dark Angel cursed Donna Troy to live countless lives, all ending in tragedy and misery. When Wonder Woman, Hippolyta, and Wally West try to rescue Donna from Dark Angel, the villainess wipes her from existence rather than let her go. Donna is remade through Wally's memories of her before regaining her memories a handful of years later.
In the lead-up to Infinite Crisis, readers learned that Donna is actually one of the few beings who survived Crisis on Infinite Earths with her memories intact, making her a timeline anomaly. Her status as an anomaly led to her multiple different origins as the universe tried to fit her into the new timeline. Also, Dark Angel is, apparently, Donna Troy from an alternate universe where she was raised by the Anti-Monitor. Donna would go on to exist on the edges of the DC Universe until it was rebooted.
When the New 52 continuity took over DC, Donna Troy was nowhere to be seen for some time. She was eventually reintroduced into Wonder Woman's mythos, but as a being created to destroy Wonder Woman completely. This new origin was further complicated when Donna went on to interact with past titan members and act as though she knew them well. Even ignoring how that made little sense given her new origin, it was also contradicted by the dubious canonicity of past Teen Titans teams. Finally, complicating matters further, the Wonder Woman storyline The Lies claimed that the new New 52 depiction of Donna Troy as a villain was an illusion but that she was still created to kill Wonder Woman.
Donna Troy shows the complicated nature of continuity in comic books. The multiple origins make a theoretically simple character into a trove of contradictory histories and retconned twists. It is telling that when the character was brought to live-action in Titans, her first and simplest origin was used. Complicated backstories and shocking revelations don't make characters compelling when they don't mean anything. Donna Troy is a compelling character for many reasons but her conflicting origins have only ever distracted from that.