This incident happened to my sister in-law when her grandma just passed away a few years back. She is actually the coward type and would never imagine herself to be at any funerals and seeing dead bodies but until her grandma passed away her fear was overcome by sudden braveness. During the funeral she helped out in everything including cleaning the dead body before it is wrapped in shroulds/white cloth to be buried later(in accordance with muslims rituals). Her nightmare began a day after the burial. She began to see her dead grandma still wrapped in shrouds/white cloth standing at one corner of the bathroom looking at her while she is bathing and sometimes at the corner of the kitchen.
Soon after she seems to see it almost everywhere in the house. She was shaken with fear,lose her appetite and couldn`t sleep well. Apparently the “thing” is following her everywhere. She was told by a relative that in order to stop the haunting, she has to use back the soap which has been used to clean the body of her dead grandma but of course the soap has been discarded! Finally, one malay medium gave her some holy water to drink and soon after the haunting stopped.