I'm so sorry.
We participate in a sport that is high risk, no matter how diligent we are to be careful, and ride safe.
I doubt there is anything she could have done to avoid the accident. On my daily commute, and on each ride, I try to appreciate the joy of riding, and at the same time realize that "today might be the day".
In spite of my earnest attempt to acknowledge the risks involved, I still choose to ride. I love riding, I'm sure your friend did too. It is the risk we share for the sport we love.