I think that anyone who has been in a bad situation generally has a "pat" story they tell about it. When it's something horrific, the details are not all there, but you have to tell something, and people ask too. I think people do form a basic story about what happened and how they feel.
Maybe you can write on a basic example of something the class might consider a bad situation, without writing on anything traumatic or going into too many details. I'm sure you will have some fellow students who write on things that they felt were horrible, and they are really not so big, you know? Don't overthink this, maybe find a safer incident and play it up, for the creative writing aspect?