^ You shud play surah baqarah in that house everyday, and recite ayat-ul-qursi as well as surah-e-naas and surah-e-falak. You shud also seek help of a genuine Aalim/Aalimah that can give specific wazeefa's in removing whatever the calamity.
Thanks Gina: But what if the Black Magic is being performed in her husband's house? She has no access to that house, not does she communicate with anybody? Do you think there would be such a wazeefa that could still help her?
May Allah reward you insha'Allah.