You actually don't need the watermelon, just good timing and intentionally looking at her in the right spot, can do this about every time if practiced enough (Btw, Headteacher can possibly let her out, Mr. Cleany if you littered in that classroom).
I asked this since you described this particular thing...Marzia and opening doors. Thought it was just me.
Do you skip the last language notebook before the chase? How many numbers on average can you save to the elevator? Asking so I can help.