A mouse! Sound the alarms. Her fiancé readies the mouse trap and cheese. Next day, the cheese is gone, and the mouse is still running free. She asks someone who knows and is told that peanut butter bait will catch a mouse. She tells her fiancé this information. But he shakes his head and replaces the cheese. This is what you use.
She thinks of their future. It will definitely have more mice-like trials and traps. His opinions will not be changed by good advice. She knows this now. Sound the alarms.
She alone understands why a mouse stopped the wedding.