thats not the worst she could have done to be honest.
Imagine getting haunted with no escape, just a simple thing like regularly scheduled jump scares would ensure he couldn't function in society anymore and would most likely be admitted to a mental asylum
If she really wanted to fuck with him, she would have paced her haunting in a way that made him recover from time to time, only to then increase the pressure suddenly again. Also make it so that he is suicidal but also under professional watch, so he has no easy way of killing himself.
Once he inevitably will finally die, his mental state will have detoriated to mush, and she won't be in risk of afterlive revenge
7/10 not enough Mental Trauma, Ghost Girl needs to level up