I think perhaps it is possible her response was due to preparing herself to handle the fallout/discussion from csa in a group therapy situation or because of what she knew about the speaker or because of what she knew about the listeners = she was thinking about and reacting to what she was possibly going to have to handle as the therapist or any of a number of other things. If I had seen what you described, I would not go to she had dealt with csa herself (your bias - wanting to protect her, know her vulnerabilities etc) but to my own bias (they protect themselves, have a horrible job and have to steel themselves to deal with a group of people who are going to react and she is going to have to contain it somehow etc.)
It is not that what you observed physically was incorrect, it is the interpretation that has more than one possibility.