Leia is force - sensitive and although, she never trained to become a Jedi, she has used the Force numerous times.
In the canon Star Wars book, Aftermath: Life Debt, Leia senses her child is a boy as well as the dark side:
"...Her thoughts reach for her wayward brother like a living thing, like branches seeking he sun. I need you here. I need your help. Luke sometimes had a farm boy's naïveté, yes, but right now she feels she could use a little of that. Her mind is a tangle of thoughts. The complexities of politics, the love of (and anger over) Han, the loss of Luke, and above all else the ever persistent worry about the life she carries--- Her skin tingles. Her mind feels suddenly unmoved from the rest of her. Leia feels dizzy enough to fall over. Oh. Oh, my! There! There it is. Washing over her and through her---and awareness unlike any she's ever felt before. A pulsing glow, flickering and strong. It's not the plant. It's not Luke. It's not even Han. It's her child. This isn't just a mother's recognition of the life inside---that she already knows....This is something separate from her. It isn't a physical feeling. It is all around her.....As such, she is suddenly aware of her child's mind and spirit: She senses pluck and wit and steel blood and a keen mind and by the blood of Alderaan is this one going to be a fighter! Wait. He? It's a boy. It's a boy. Her hands fly in front of her mouth as she both laughs and cries at the same time. This, she thinks, is the light side that Luke always goes on about---the promise of light, the promise of a new life...and then, the black edging of the dark side encircles her bliss like a noose. Because what rides swift on the heels of hope but fear--a fear that stretches out far and wide like a growing shadow....."
Through several canon comic books, Leia is seen fighting with a lightsaber and She also sees Padme's protrait turn and stare at her. She also senses Maul's presence in the palace of Theed from where he stood years ago.
In another canon Star Wars book, Bloodline, there are other examples of Leia's force-sensitivity:
Bloodline, p49
"...Leia mentally cataloged that name for later. Maybe her curiosity had only seized upon a random group of people, frequent gamblers who would naturally visit a world like this often, calmer than most. Her suspicion of them was only a hunch, but her hunches often proved to be right. Luke said those strong instincts of hers served as proof of the Force, evidence that it was working through her all the time..."
In the films, various scenes showed Leia's force-sensitivity:
Leia doesn't give away where the plans for the Death Star are located, despite interrogations and pain (Episode IV)
She knew the Millennium Falcon was being tracked (Episode IV)
Leia senses something is wrong in Cloud City and is distrustful of Lando (Episode V):
LEIA: Something's wrong here! No one has seen or knows anything about Threepio. He's been gone too long to have gotten lost. Han takes Leia by the shoulders and gently kisses her forehead
HAN: Relax. I'll talk to Lando and see what I can find out.
LEIA: I don't trust Lando
Leia hears Luke's SOS call through the Force (Episode V)
Leia remembers her mother (presumably through the Force) (Episode VI)
Leia always knew Luke was her brother (Episode VI):
LUKE: Yes, it's you, Leia.
LEIA: I know...somehow, I've always known
Leia senses Luke left the Death Star and is alright (Episode VI)
In The Force Awakens novelization, Leia senses the deaths on Hosnian Prime as the system is destroyed
She senses some light in her son, Kylo Ren (Episode VII)
She senses Han's death (Episode VII)
Dude proved Snoke didn't have him under his control and is now the Supreme Leader of the First Order. Whether Kylo is still a bytch or not, that's a W
