Im not sure how much of a bike crash expert her bike mechanic would be. I’m not a bike mechanic or an expert, but am a mountain biker who rides with lots of friends and has been with them when they crash (and crash a lot myself). Bikes end up in a lot of different ways, especially when using flat pedals that a lot of beginners use. With clipless pedals, the bike usually stays with the rider when you crash as you are physically attached with your shoes clipped into the pedals. With flat pedals, the bike normally ends up down the hill as there is no physical attachment once your feet leave the pedal, your butt leaves the seat and your hands let go of the handlebars as you are flipping over them in a crash. From what I’ve seen and experienced, on downhill crashes you almost always go over the handles bars and if not clipped in, fling the bike down the hill.