She probably has no idea that it is on.... (some kind of default or someone's stupid idea of a joke). I had a teacher in high school who had no high frequency hearing left. As well as causing lots of other misunderstandings "b" c? "b!", d? "B!!", e? NO "B!!!- AS IN BOY"...... his digital watch alarm would go off every day at about 10 min until the end of class. At just about the end of the year someone finally mentioned it. He had no clue that it was ever going off.... (and wanted to know why no one had told him sooner)