There are some good books that might help you or anyone else in the group to understand about dissociative disorders. I like http://strangerinthemirror.com/ because it shows the range of dissociation from an ability that normal people have and use naturally, through the various ways that extremes of dissociation can affect people.

When you understand a little about dissociative disorders, it will be easier to treat a group member with DID as a person like everybody else. You might also ask her how she would like you to proceed, whether she would like to talk to the group about her disorder briefly, or stick to the primary goals of the 12 Step group.