Maybe, though, it's the microwave's fault, for being unusable without a set time limit. She never uses a kitchen timer when she's using the range, so I suppose if she could turn on the microwave and use it without the timer, she would. Do they make microwave ovens like that? I've never heard of or seen one.
This talk of timers reminds me of when the landlady her current range. It has a feature not unlike a microwave timer; you could set it for an hour, and after an hour the oven would shut off. It also has a standard kitchen timer, but I failed to realize that for for the first few months after it was installed, and so I just always used the oven timer. I don't remember exactly how I figured out I was doing it wrong, but I'm pretty sure a mild burn was involved.