Necromancy.

The dark art of summoning the dead.  Why not use those hollowed-out shells of life to divine the future?  Why not use them to piece together mysteries long-since passed?  Those ephemeral corpses would serve her best if they earned each slammed door and floorboard creak or their right to their shallow home beneath the earth with the information only the dead could give.  After all, necromancy is a craft that is strangely akin to the ancient practice of calling on your ancestors for strength.

...but there the similarities end, though she was too proud to admit it (the ghosts, however, knew the truth of it all too well).  Your ancestors are of you, blood of your blood, with you always in your bones and dreams.  They offer guidance and reassurance in times of need, hover over you in peace--on their own terms.  Always on their own terms.  

But the necromancer?  She calls upon energies not her own, summons up demons to twist fate for her own purposes; conjuring ghosts to glean secrets she was not meant to know.  She is a perversion of magic.  

Balance must be restored.  Slowly, one ghost at a time, this necromancer begins to give herself over to the world of the dead, to feed the souls she preys upon.  Soon the world she once hoped to bend to her will is no longer hers, and the realm she exploits will devour her whole.

And so she might feel powerful now.  She might win her small battles drawing on the shadows and forcing stories from freshly-awakened souls.  She might even reach a parody of contentment in her life, happy under her illusion of control.  But the dead are listening.  The dead are always watching.  And they will exact their price.