I stopped to render aid adn she kept saying she looked into her mirrors and did not see him. Two points:
1. A car, truck, or suv is easier to see, it is bigger.
2. If in this case a tahao runs up the side of my jeep cherokee at 30 mph I have an excellent chance of little or no injury. There is nothing between you and them on a motorcycle.
Again, she could just as easily not see the other vehicle. Especially if she was distracting herself. The bike was probably in her blind spot. Cars can be there too.
Also when you are on a motorcycle and something like that is developing you have more options to evade than you do in a car.