The movie's tagline (which you can see on the image in the main page). "When a girl has a heart of stone, how can you melt it? Just add ice." You might just let the nonsense of melting something with ice pass considering it's a pun, but how can you melt something made of stone?
Technically possible with some stones, although large amounts of heat are required. It just makes the statement even more hilariously wrong.