I would just like symptoms and/or adjectives about a character when they might suddenly get sick because of a traumatic experience.
I just don't know how to describe the character and this is a vital part of my story. She is actually getting her mind touched by a demon and that will cause some serious shock, if not PTSD. The "presence" sticks around and she doesn't get the PTSD until the very end, but it's still a serious shock for her.
The shock is not immediate, but it shows on her face and through physical symptoms. Not having a real-world illness to draw from, though, I'm unsure of what those symptoms may be, or how to show her discomfort.