First, you have to understand the problem. She has an inferiority complex here and a lack of self confidence. She wants so bad to be the center of attention that she will do just about anything that will draw attention to her and she knows she has the gift of gab. The best thing here is not to egg or urge her on so best to ignore her and let her realize that others don't want to listen to her at all and don't ask her questions so she can keep going.
Sooner or later she will catch on that she is the problem when no one wants her around which is sad as she may be a pretty good person otherwise but has to learn when to keep her mouth shut and she may even need professional help to overcome her inferiority. Hope this helps a bit