Take a proficient fencer, then shoot him in the chest with a 12 gauge shotgun slug, then see how well he fights afterwards.

I’m guessing not great.

Rey obviously knows a bit about melee combat because she handles multiple attackers at once on Jakku.

As I’ve said multiple times before, her basic scrappiness coupled with Kylo’s having tanked a round from a bowcaster which generally sends people flying, plus her obvious latent strength in the Force explains the fight perfectly well.