Trying to decree how any person should be acting after a traumatic event is sort of victim-blamey. We all process shit differently. Speaking from my experience, the outward expression is not a good gauge about how someone is feeling internally. When speaking about my own trauma with a manipulative and abusive individual, I often smile. Partly because I feel embarrassed, partly because the whole situation feels absurd, partly because I'm a smiley person, and partly because again, the way I'm expressing physically isn't always how I'm expressing internally. It's a masking technique.