This is probably one of the most frustrating missions for me. Susan seems highly bugged and would wander around aimlessly. Anyways as soon as the chapter starts head through your parent's bedroom and downstairs to the lobby.
Chances are you'll meet Susan on the way and you'll receive your target confirmation. When you get to the lobby head down the stairs and enter the room on the left side of the stairs.
Inside the laundry room you'll see a cross at the left side wall near the baskets. Turn the cross upside down so you can use your powers.
On to the main mission. Approach the washing machine and open the lid.
Now look at the shelf on the left side of the washing machine and use your telekinesis on it. Drop the iron inside the machine and close the lid on it. The washer should break and Will will come and fix it.
Wait for Susan to go inside the laundr room and interact with her until she asks you to go and check if the second floor bathroom is unoccupied.
Now climb back upstairs but instead of going into your parents's room turn right and follow the corridor to the end. Enter the last door at the end of the corridor to enter the bathroom.
Inside the bathroom there's a cross near the toilet. Turn it upside down and wait for Susan to go inside the bathroom. This is what I found so annoying, Susan doesn't seem to want to stay in the bathroom for some reason.
I'm not sure about this but it worked for me. When Susan goes in the bathroom, leave then shut the door behind you and stand in front of it until the cutscene starts.
Once the cutscene plays head inside the door on the right side of the bathroom door. You'll end up inside Tom's video room.
Interact with the poster (woman with a green background) beside the monitor and you'll find a small peeping hole underneath it.
Peep on the hole and you'll see Susan taking a bath. Equip your telekinesis ability and use it on the blow dryer on top of the sink counter.
Now drag the blow dryer over to the bathtub and drop it in the water to electrocute Susan.