How good Rey is with the force doesn’t have a good explanation in the movie, maybe i’m making excuses, but i enjoy trying to fill in these kind of plotholes, so here’s my theory:
Us humans, if put in a situation of danger, make adrenaline, wich can increase our physical streanght for a limited amount of time
Maybe the force works in a similar way, Rey was in danger, midichlorians went into overdrive, and her force powers increased temporarily