Find out if these things really did happen to her, or if they are just dreams. If they really happened to her (or something similar, that was of an abusive nature) then try to offer to help her get some therapy to deal with the anxiety.
If they are, indeed truly just dreams and nothing more, then tell her that most people often have horrific dreams when they are under a lot of stress and then tell her to avoid drinking alcohol or eating spicy foods more than a few hours before she goes to sleep, because all of those things can contribute to bad dreams. Ask her if she would like to change her bedroom routine. If she says yes, tell her to stop eating or drinking at least 4 hours before bedtime, to stop watching TV at least an hour before bedtime, and only to read pleasant stories before she goes to sleep. She also might want to participate in a relaxing yoga routine about an hour before bedtime and then listen to some soothing, relaxing, sleep inducing music while she goes to sleep.
If she just wants to kvetch. Tell her you are not interested.