Along with everyone, I'm also hoping for a speedy recovery for Lena.
I think you are going to have to be patient with her about getting back to riding. Since she can't recall what caused the fall, it is just human nature to be even more insecure about it.
I had a similar experience with a serious car accident. The guy came out of the blue and hit me (blind intersection). After getting out of the hospital, the first thing I wanted (needed?) to do was to visit the 'scene of the crime'. What I hoped to see was some kind of a reason for me to blame myself for the accident. If I could do that, I could convince myself that I just need to be more careful, look for this or that, and I can keep myself safe. But it wasn't there. It was a blind intersection, and if someone blows through their stop sign just as I get there, I get hit, and there is nothing I can do about it. It is very unsettling. Sticks with me to this day.
While this is far from being a test-pilot, I remember one of the messages from the book "The Right Stuff". Whenever a test pilot 'bought the farm', or 'augured in', the other test pilots talked about how he must have made some dumb mistake. It's a self-defense mechanism - if we convince ourselves that it happened because the other guy was careless, then it can't happen to us, because we are on top of it. But sometimes, stuff just happens. That is hard to process.
So glad she had that helmet.
-ERD50