Spoilers for The Last Jedi ahead. We've always known, on some level, that when the midichlorians were flowing between Luke and Leia's parents, both twins got a piece of the pie. Of course, one twin (Luke) got a lightsaber and a few Jedi masters along with his slice, while Leia got a seat in government and about a million other cool jobs, all of which were, alas, saber-less. But in The Last Jedi, Leia uses the Force, big time. But after all this time, and after JJ Abrams explicitly told us she chose not to learn the ways of the Jedi, how can Leia use the Force in The Last Jedi?
Well, here's the thing. One of the major points of The Last Jedi is that in order to be a Jedi, you don't really have to read all the texts and got through all the training steps passed from from the Jedis of the past. In fact, Yoda (as a Force Ghost) straight up burns down the last remnants of Jedi teachings with glee, because it doesn't matter. Even without any fancy formal training, Rey is already a Jedi (Luke pretty much confirms as much when he tells Kylo Ren that he's not the last Jedi, moments before his death). Hell, at the very very end of the movie, we watch as a wee little lad, forced into rigorous work on the casino planet where Finn and Rose find their coder, hops about and uses his innate knowledge of the force to toss around a broom playfully. Knowing how to use the Force isn't something you study, it's something you have within you.
So, that being said, it's pretty clear that Leia simply has it in her. Sure, we've never seen her use the Force in any way other than to feel things (Han's death) or hear things (Luke calling for help from the bottom of Cloud City at the end of Empire Strikes Back, and again in The Last Jedi). We've always known our girl was majorly Force-sensitive. Now we know she also knows how to wield the Force as well as she knows how to feel it.
And that is, frankly, freaking awesome.
It confirms what many female fans have always hoped for their Princess-turned-General: That she's just as strong, just as special, just as "chosen" as Luke ever was. She's always been the serious one, the level headed one, the one who gets sh*t done. And while the strong, dependable leader is an important role, and one so many of us admire Leia for, it's admittedly not the "fun" role. Now that we know Leia can manipulate the Force — aka do the fun stuff — everything has changed.
Of course, those fans who've read the canonical books released alongside the films probably saw Leia's big move coming a mile away. In 2016's Aftermath: Life Debt, Leia appears to use the Force in grander ways than we'd ever seen before. In the book, 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." The book also betrays that Leia got some slight training from Luke regarding using the Force.
Lucasfilm doesn't let any detail, especially a Skywalker detail, drip through unless it means something big. And by the time we see Leia being her own damn hero in The Last Jedi, and pulling out a feat bigger than anything we've seen on screen from Luke, it's clear that Leia is just as powerful as any Jedi.
Tl;dr: Hell yeah, she can use the Force, and if you're still confused, you simply haven't been paying enough attention.