It kind of sounds like something may be amiss with her. Who knows what it is. If she comes to the group, perhaps you could talk to the group facilitator about the issue during a break or afterwards (or via email).

Must this person be in your life? If she is in a class or work, just separate yourself from her. If she won't leave you alone, perhaps take her aside and let her know in a serious but uncruel way, that she is triggering (or whatever) and you'd appreciate distance from her.

If she needs help, someone should encourage her to seek a doctor or therapist.