Hogwarts Couples!!! discussion

Cedric's directions to Harry on how to reach the prefects' bathroom were extremely clear: "fourth door to the left of the statue of Boris the Bewildered on the fifth floor" (GF23). The door requires a password, and can be bolted from the inside. No mention is made of any portrait or statue guarding the room's entrance; apparently the door itself recognizes the password. There is one piece of artwork in the bathroom itself, however, a rather flirtatious picture of a mermaid on one wall (see). Myrtle, who occasionally enjoys spying on the prefects as they bathe, doesn't seem to like her much.