I'm sorry to hear of Lena's accident. I hope she makes a full and speedy recovery.
I've had a couple of serious bicycle accidents over the years, and one of them resulted in a concussion, unconsciousness, and amnesia. Neither accident involved another vehicle. I have no recollection of the accident which resulted in unconsciousness, but I was with a friend who saw what happened (a broken fender caused the accident). When I woke up on the road in a rural area, I couldn't retain any information, like Lena apparently. My friend said I asked over and over where I was and what happened. By the time I got to the hospital, I was able to remember I had already asked the question, but I couldn't remember the answer. I thought the whole thing was a bizarre dream until I woke up the next morning and recognized my surroundings from the evening before. In fact, I had amnesia covering a period of about 3 months prior to the accident. Everything beyond 3 months in the past, I could remember. But for the 3 months in the immediate past, nothing at all. From 24 to 48 hours after the accident, those long-term memories all gradually returned. That was a very odd experience.
After 48 hours in the hospital, I was released and my friend and I got a ride back to the site of the accident where our bikes were being stored in a farmhouse. I could remember riding on the same road up to a certain point perhaps a 5 or 10 minute bike ride from where the accident took place. The memory from that point on to when I woke up on the road will never return. I have read that that is normal for a concussion like mine. I suspect the same will be true for Lena.
In my case, I wasn't afraid to get back on my bike. Indeed, I had to get back on my bike because we were in the middle of nowhere when I had the accident. Most of my visible injuries were in my face. I had stitches in several places on my face and lots of bloody scabs. Over the next few days, maybe weeks, people stared at me everywhere I went. It all eventually healed remarkably well. To this day, anytime I perceive someone near me who is disfigured in some way, I avoid staring at them out of respect.