WARNING: This post contains spoilers for Aftermath: Life Debt
In Return of the Jedi, audiences learn that Princess Leia Organa is Luke Skywalker's twin sister. As the daughter of Anakin Skywalker, it means that Leia is Force sensitive and has the potential to be a Jedi Knight if she so chose. Of course, the siblings went down very different paths following the Battle of Endor. Leia became a leading figure of the New Republic before assuming command of the Resistance; Luke went off on a quest for the lore of the Jedi and exiled himself on Ahch-To once Ben Solo became Kylo Ren.
Still, Luke mentions to Leia, "In time, you'll learn to use it as I have." As fans have seen with Maz Kanata in The Force Awakens, it is possible to know the Force (and control it) without becoming a full-fledged member of the Jedi Order. It would appear that Leia fits that bill, if passages in the new canon novel Aftermath: Life Debt are any indication. At some point, Luke taught his sister some lessons, which play a substantial role in the book.
Leia using the Force isn't exactly a new topic for Star Wars to cover. When Kylo Ren killed Han Solo in Episode VII, a cutaway shot showed that Leia felt a disturbance. Even in The Empire Strikes Back, she hears Luke's call for help and brings the Millennium Falcon back to Cloud City. The biggest takeaway from Life Debt is that Leia received some minor training from Luke, specifically how to let the Force guide you during a troubling time. In the novel, Leia is going through a very stressful period, as Han has gone missing while trying to liberate Kashyyyk with Chewbacca (and the New Republic offers minimal help to find him).
Life Debt made headlines prior to its release thanks to an excerpt that depicted Leia communicating with her unborn child and realizing that she's pregnant with a son. This is perhaps the most noteworthy example of the Princess using the Force in the book, but it is far from the only one. During a dogfight sequence towards the end (when Leia is flying the Falcon against an Imperial attack), author Chuck Wendig writes, "There are even moments when she can feel the battle unfolding around her in space - invisibly, as if all of it is a warm stream in which she has dipped her hand." Leia may never have followed the footsteps of her brother, but she is using her abilities in ways that benefit her, letting the Force flow through her when it's absolutely necessary.
The Disney canon hasn't been afraid to suggest Leia has become somewhat skilled with her gifts. There are instances in Claudia Gray's Bloodline that imply Leia is using the Force as she works on unraveling a diabolical plot. She isn't performing Jedi mind tricks or levitating objects with her mind yet, but there's enough evidence in the publications to suggest that Leia has become (or is in the process of becoming) strong with the Force, and it will be interesting to see if this aspect of the character is developed in the future. Leia has always been a powerful fighter, but now that she has the Force as her ally, she can take things to a whole other level.
A big question is whether or not Leia's developed use of the Force will factor into one of the upcoming movies - beyond the small segments already seen. The Lucasfilm story group is very careful about what they release and when they publish it, so it's likely they have some plans for Leia in Episode VIII or Star Wars 9. At the same time, her role in The Force Awakens was very minimal, and if rumors about Star Wars 8 pan out she won't have much to do in the next chapter, either. It would be disappointing if Leia never got to display the full extent of her talents on the big screen, but at the very least, fans are getting a taste of a Force enhanced Leia in the other materials available, illustrating that Lucasfilm is making the most of their initiative.
Rogue One: A Star Wars Story opens in U.S. theaters on December 16, 2016, followed by Star Wars: Episode VIII on December 15, 2017, the Han Solo Star Wars Anthology film on May 25, 2018, Star Wars: Episode IX in 2019, and the third Star Wars Anthology film in 2020.