That’s not the next time she shoots. She hits another trooper with one shot, and that was with a quick turn-around shot no less. As for Kylo Ren, it had already been established in the movie that he can use the force to manipulate fired blaster bolts, to the point of even freezing them in mid-air for an extended period of time, so there’s no way to know if her aim is off or if he’s altering the course of the bolt.
Next time she even fires a gun is when Han is killed and her aim is all over the place. Finn is also firing and yet they only manage to hit 2 troopers, and that could have been Finn hitting his mark.
They don’t even show where her shots were going in that scene. They showed her firing but kept the camera on her, and when they did cut away they showed two troopers getting shot, with no indication of who fired the shots. In other words, that scene is irrelevant, because the camera didn’t show whether she hit anything or not.
So, apart from hitting two troopers with 3 shots (not exactly expert and the second trooper wasn’t exactly a quick turn around shot either) you make excuses for the other two times she shoots at anything. So where the hell is there any indication that she is an expert? Your excuses actually show that there is no way to know if she is a good shot or not. I wonder if you say the same thing about Luke, who had NO combat experience, as far as we knew through the film had never fired a gun before, yet was able to expertly shoot out the door controls from the other side of the hangar bay with one shot?