Rey did the number one thing Yoda stresses in his training with Luke.
Clear your mind.
Ren, was struggling with the light and the dark side of the force, pain from Chewy's attack, anger over "the traitor" (Fin) causing all of their plans to fail, as well as killing his Father which didn't give him the feeling he was looking for.
Rey was just afraid.
She was always a good fighter, because she had to be to survive.
Once she got over her fear of Kylo, she simply handled shit like she normally does. Only this time assisted with the power of the Force.
the Force isn't someone who can twirl a lightsaber better,even though that's what the prequels want you to believe.