Warning: Spoiler! (Click to show)
Originally Posted by Ataturk
I take it all back. Upper body strength, reach, mass, speed -- insignificant next to the power of the force (of political correctness).
This is the same universe that a young man with barely any training managed to use the force to make a pinpoint accurate shot to without his tracking screen to blow up the first Deathstar. The fact that it bothers you so much that a woman could defeat a man in combat using the force says worlds about you more then anything else. Let's ignore the fact that Kylo had been badly wounded by what was shown to be one of the most powerful handheld weapons in the movie, was suffering the emotional distress of just killing his father and just fought another "able bodied male" moments before.
Even ignoring all that, there is plenty of subtext in the movie that Kylo might not have been all that invested in killing her. Speculation can go wild here, but I suspect if this proves to be true it will become clear in Ep 8.