This is the correct answer.
A prank should be funny and enjoyed by the person getting pranked.
OP. Using things she's deeply afraid of to "prank" her is not going to be enjoyable by anyone except you. You want "psychological horror"? Have someone call her and your family pretending to be the police department and say that you passed in a vehicle accident. Point a gun (fake or not) at her and pull the trigger. Find some roadkill and put it in her mailbox, then car, then bed. Have some friends stalk her at her work or school and then follow her home. Lay on the floor with an empty bottle of sleeping pills and a note that says "I'm sorry".
See how funny those pranks are!
Time cube. I think about this some times and wonder... https://web.archive.org/web/20150506055228/http://www.timecube.com/index.html
https://en.wikipedia.org/wiki/Time_Cube