Do you believe a persons true character comes out in a stressful situation?

So the other day we were in a wreck with my boyfriends brother and his girlfriend. None of us got hurt but she screamed bloody murder the whole time. During the accident and even after even though none of us had been hurt.  In her defense it was quite terrifying. I mean her boyfriend blacked out behind the wheel because he had low blood sugar and we slammed into a cement wall. Scared the living shit out of all of us but she was the only one screaming. That's all she did, scream. In the time she was scareaming I told my boyfriend his brothers foot was still on the gas and he grabbed him and moved his legs just enough that his foot wasn't on the gas he then looked for some kind of food to give him because he couldn't even talk or lift his headi . but the thing that really bugged me is that she couldn't get herself under control and handle the situation like an adult. We even had to talk to the police and tell them what happened even though we didn't own the car nor were we driving. In her panic attack we had already started to get control of the situation. She just screamed bloody murder like she was being stabbed to death the whole time and it was so bad people started coming out of their houses and people stopped their cars and assumed we were hurt badly because of the screaming. Someone even grabbed her and told her "get your shit under control"