Rip Lauren, but OP why make a point of saying 'her own horse' what difference does that make? it was an accident and could happen to anyone on any horse, not like the horse did it on purpose or maliciously, which is kinda how you made it sound.
:-( yard rule at our place, we have to wear a hat when putting out or fetching in.
Just to clarify a a couple of inaccuracies in the report there;
- Solo hadn't "escaped from the field", he had been being led up from the field and then was seen loose on the track.
- The "stable hands" who found Lauren were her friends. And she wasn't supposed to be "on his back" as he was being led in from the field, not ridden, at the time.
- No one was with her at the time, although she was found very quickly afterwards, so no one can be sure exactly what happened, they don't know that he "lashed out". He is a very easy horse to handle on the ground, a big sop, and this apparent incident is very out of character. She may well have tripped and been accidentally stood on when she fell over.
She was a friend of mine as I kept Hopalong on this yard until August last year. I'd known Lauren about 3 years and she was a genuinely lovely girl. She would ride Hopalong now and then when I was away and she was a really lovely, quiet and talented rider. Still feels unreal and everyone at the yard is still in shock.