In an alternate and much darker Star Wars timeline, it was proven that Leia would have been the better choice to become a Jedi over her brother Luke Skywalker. As seen in Dark Horse Comics' Star Wars Infinities miniseries - which imagined what the original trilogy films would have been like had things gone differently - the Empire Strikes Back storylines sees the timeline shifting after Luke Skywalker dies on Hoth, resulting in Yoda teaching the ways of the Force to Leia instead.
Effectively being the Star Wars version of Marvel's What If...?, Star Wars Infinities: The Empire Strikes Back was a four-part miniseries that featured Luke's early demise on Hoth. Rather than surviving his encounter with the monstrous wampa, Luke was instead mauled and survived just long enough to tell Han Solo about his vision to go to Dagobah and become a Jedi. Initially believing that Han was meant to learn the ways of the Force, the crew of the Millennium Falcon traveled to Dagobah only to learn that Leia was Luke's sister and that she was destined to become a Jedi in his place.
Not only does this series - from Dave Land and Davidé Fabbai - play off of Yoda's comments to Obi-Wan that there was another besides Luke who could save the galaxy in the actual Empire Strikes Back, but it also supports the idea that Leia would have been the better option. As seen in the miniseries' fourth issue, Yoda is very impressed with how quickly Leia learns, claiming that she's learned more and grown further than any Jedi he's ever trained before. This can largely be attributed to her more disciplined upbringing as a princess and senator on Alderaan, which later saw Leia becoming a critical leader of the Rebellion. This is starkly opposed to the farmboy life Luke had, which made him too reckless and impulsive according to the diminutive Jedi master.
Leia's prowess as a Jedi in this alternate timeline pairs well with the canonical fact that Yoda originally wanted to train Leia over Luke. In From A Certain Point of View: The Empire Strikes Back, the anthology novel features a story where Yoda begrudgingly gives in to Obi-Wan's requests to train Luke. In his mind, Leia was the far greater choice, and someone he felt already possessed more traits that were well-suited to a Jedi knight.
While Luke himself would eventually train Leia following the events of Return of the Jedi, this non-canonical series provides an exciting look at what might have been. Although Leia's Jedi training was the dark result of Luke's death in this particular miniseries, seeing her evolution as a gifted student under Yoda proves she would have been just as capable of restoring balance to the Star Wars galaxy as Luke Skywalker (if not more so.)