Cleanse a few rooms, as a starter...ward them, nd make them 'safe havens' for her. I'm not sure it would be a good idea to tell her, even if you manage to convince her to stay, she'll be even more scared...it'll make it very tough for her to be alone there...

Also, after cleansing those selected rooms, make it perfectly clear for all there, that any more incidents will lead to more off-limit areas...while good behaviour might, in time, lift a few wards...