Mistake?

When my sister was in 5th grade her teacher was called Miss Taake. She was ugly and mean to the children. Sometimes she would leave the children in the room by themselves when she was supposed to be teaching them. Then, if they got noisy or ran around while she was gone, she would punish them when she got back. The children called her "Mistake" because she was mean and nasty.
But here's another part of the story. Grandpa's Uncle was in Miss Taake's class in second grade, more than 20 years before my sister. At that time, he says, she was young and beautiful and all the children loved her. Then at the end of the year, she got married and, since at that time, around 1932, married women were not allowed to continue teaching, she didn't come back to school.
But she was still Miss Taake years later. What happened? Did she get married but tell the school she was not married? Or did she decide not to get married? Or did she get married and later get divorced? When did she go from being young and beautiful and kind to being nasty and old and ugly?
This is all a mystery. Or maybe there was some mistake.