In an apartment?! This woman wasn’t very creative.
How about using the tank lid as a battering ram, or to knock off the door knob? If the floor below is a neighbor ... flood the bathroom! Run everybody out of hot water to force an investigation!
Doesn't matter even if she's on the ground floor. When water starts running out the door, somebody will investigate.
Everyone should learn SOS in Morse Code. Random banging on a pipe is obviously not very effective.
Door hinges are usually on the inside; a flathead screwdriver might be useful, but easier than that is to not lock the door. What’s the point, when no one else is around?
From what I’ve seen of French bathrooms on House Hunters, there probably wasn’t room to swing a tank lid, if there were a tank lid to swing. Some French toilets are tankless.
That would be...
her own personal Waterloo.