Black water sister / Zen Cho.

Ah Ma may be dead, but she's not done with life yet . . . When Jessamyn Teoh starts hearing a bothersome voice in her head, she chalks it up to stress. And who wouldn't feel stressed, in her position? Broke and jobless, she's abandoning America with her parents - bound for Malaysia. She left when a toddler, and hasn't been back since. She soon learns the new voice isn't even hers, it's the ghost of her estranged grandmother. Ah Ma was a spirit medium, avatar of Black Water Sister, a local deity. Now Ah Ma's mission is to deal with a gang boss who offended her goddess - and has decided Jess will help her. Whether she wants to or not. Drawn into a world of gods and ghosts, family secrets and dangerous dealings, Jess must fight to regain control of her body and her destiny. If she fails, the Black Water Sister may finish her off for good. And all the while, she has to stop her dead grandmother from taking her body out for a drive at night, scribbling graffiti on her aunt's walls and spying on her personal life.