The pipes bit is actually the thing that seems most improbable to me. Pipes break when the water in them freezes, which occurs when it gets cold and the water isn't flowing.
Unoccupied cottage in the woods? Pipes will freeze. Unoccupied apartment sharing 5/6 walls? Plenty of heat from neighbors, pipes do not necessarily freeze.
And about the windows, well she probably shut the windows when she left (not sure how it's called in English actually? closing the wooden things that cover the windows).
Accidents do happen, but an unoccupied apartment that has not had a water problem or a broken window in 70 years? I don't see a problem, especially in such a non-hostile environment.