Your friend was not paying sufficient attention to traffic while walking on the street and got hit. Because of that, now her friends and family are worried about her. If she had returned the calculator to you one of the previous many times you asked, this would not have happened.

Ultimately, we are responsible for ourselves. We have to stay in the minute, pay attention to our surroundings and think about our actions. If we are thinking about something else we are not paying attention in the moment. If we are going to daydream, we need to make sure our surroundings are safe. She was probably thinking of all the places she could drive now that she has a license, was probably not thinking of you and the calculator at all (getting a calculator is kind of boring, I'd say; at least would be to you and me who have had driver's licenses for a longer time :-) and was not thinking about the traffic on the road, either. It is in no way your fault, you were not there; she and the driver of the car are responsible for not paying attention to one another and what actions they were performing.