The Death of Superman was one of the most monumental events in the history of the DC Universe, and many heroes participated in the initial battle against Doomsday alongside the Man of Steel. While the Justice League of the early '90s jumped to Superman's aid, one of DC's biggest heroes, Wonder Woman was noticeably absent from the event in comics.
Although she was part of the fight within the DC Extended Universe, Wonder Woman was busy offworld during Doomsday's comic book rampage.
Created by Dan Jurgens, Jerry Ordway, Brett Breeding, Roger Stern, and Louise Simonson, Doomsday first appeared in Superman: The Man of Steel #17 in 1992, although his destructive rampage throughout the DC Universe didn't begin until a few months later. The monstrous Kryptonian first battled the Justice League International, with Guy Gardner's Green Lantern, Booster Gold, Ted Kord's Blue Beetle, Maxima, Fire, Ice and Bloodwynd, who was Martian Manhunter in disguise. Booster was unintentionally responsible for giving the creature its name when he remarked that "it's like Doomsday is here."
Superman was occupied in an interview with Cat Grant when the battle began but left immediately as soon as he heard it. As a testament to its power, Doomsday overwhelmed the team without its full abilities, as it was still partially bound within an assortment of ancient cables. When Superman, Guy, Fire, Bloodwynd, and Booster launched a combined attack it backfired and freed the monster completely. The rest is history, with the Man of Steel falling in the landmark Superman #75.
While this eclectic lineup of the League was ultimately not terribly effective, Wonder Woman is one of the few heroes who could've been strong enough to turn the tide, possibly even preventing Superman's death.
In Diana's defense, she wasn't even on Earth at the time of Doomsday's attack. Shortly before Doomsday's rampage began, Wonder Woman #66 by William Messner-Loebs, Paris Cullens, Robert Campanella, Matt Hollingsworth, and John Costanza kicked off a months-long storyline in which Diana and Russian astronaut Natasha Teranova were lost in space, abducted and brought to Hope's End, a prison planet full of people enslaved by the alien Sangtee Empire.
Eventually, Diana and Natasha managed to stage a revolt that led to the end of slavery in the empire, but by the time Diana returned to Earth, Superman was dead. She was present for his funeral along with most of the other major heroes who had been missing from the fight, such as Batman, Supergirl and the Flash.
The cinematic death of Superman featured in the film Batman v Superman: Dawn of Justice saw a much smaller, more exclusive team in the battle against Doomsday. Diana fought alongside Superman and Batman, despite having been reluctant to operate as a public hero following Steve Trevor's death. Lois Lane contributed as much as she could, locating the Kryptonite spear Batman had forged, which Clark eventually used to kill Doomsday before the monster killed him. The Martian Manhunter observed the battle in his guise as U.S. Secretary of Defense Calvin Swanwick, but he did not directly participate.
After the battle, Diana and Bruce Wayne attended the private funeral held for Clark Kent in Smallville, rather than any of the public tributes. While watching the service Bruce told her of his belief that they needed to form a team of superheroes to protect the world from future threats, leading into the events of both versions of the Justice League movie. The two-part animated Death of Superman film set in the DC Animated Movie Universe featured a more standard, higher-powered version of the League facing Doomsday, with Diana arguably putting up the most significant opposition to the monster before Superman got involved.
As those latter two examples prove, Wonder Woman could've made a real difference in the battle against Doomsday. However, she just happened to be far away from Earth when Superman needed her the most.