Maybe an "even if" argument, even of we grant you premise, it doesn't work.
We have to see the prosecution crash analysis.
I would point out that my understanding is Karen has said she did a 3 point turn. A reversing impact as part of a 3 point turn, would better explain the direction of where John ended up, as she would be reversing across the road towards him, and the direction of force and momentum would be a better fit. But it is hard to see a 24mph speed achieved, and she would have hit the curb at perpendicular manner. Although the 24 mph, may be an overstatement, as the car maybe measuring speed based on wheel movement, which on an snow/icy road with lower traction may be more spin and less speed.