It seems a bit paradoxical that the very act of attempting to talk about trauma might actually trigger trauma, and turn out to be "too much" for the traumatized person to handle, but this can be the case, according to Belleruth Naparstek, in her well-regarded book, "Invisible Heroes: Survivors of Trauma and How They Heal." She writes:
Clearly, we're just scratching the surface here of a much larger topic. But while the case can be made that listening to another deeply is often quite therapeutic, having to talk about (relive) something traumatizing might have adverse effects.