That sounds really painful, silently. I don't know what DBT group therapy is, but is a part of it that the group members have to run their own group rather than relying on the facilitators for help? Maybe the faciliators were just waiting for the group to say "enough already, shut up lady." I hope you won't let this one woman ruin the group experience for you. Maybe at the next session, you can raise the topic. Could you say, "last time when Ms. X went on her tirade, I was very hurt, and I felt like the safety and security of our group was compromised because of her behavior. What can we do about that?" And then the group could discuss, and maybe put Ms. X in her place and let her know her destructive and hurtful behavior will not be tolerated?