Is there someone in the group with leadership qualities, who could take the initiative, and when she starts talking about herself, make a pointed remark, like "Cathy, it sounds like you travel a lot" (if she was talking about travel, for instance) Or "Wow, you must go shopping a lot"(if she talks about things she buys) and then say, to someone else, "Joan, I wanted to hear about your trip to Las Vegas" -- in other words, turn the conversation away from her. And if she butts in again, "I really want to hear what Joan is saying right now." And have a few people and topics you REALLY want to hear about at each meeting.
It would take someone with a strong personality, but maybe CC would get the point.