I think you're right that kitchen mishaps can happen. She should practice safety methods. I have left a gas burner on for hours in the past. Now, though OCD-like, I always practice a ritual of looking at the oven and burners to confirm "Off, off, off, off, off!"

Have you asked your wife why she cooks/bakes at night? If not, it's recommended even before asking us. Perhaps this should be mentioned to her psychiatrist. Or, has she been a night owl for a long time? Any other hypomanic/symptoms along with what could be insomnia and goal/project-driven behavior?

I find time alone in a quiet slightly dark house quite thrilling, sometimes. It's almost a "When the cat's away, the mice will play" situation. Also, I love breakfast, but am often not motivated to make anything special at 6 am. If I am at 3 am, then I wake up that last time to a big treat (muffins, cake, etc). The house smells yummy and it's like a holiday. Definitely feeds a touch of euphoria.