She is a teacher but as you expect she is not a statistician. If she would have studied statistics in statistics department for a year she would know what to teach. First you start with a coin, you have 1/2 chance to get this and that etc. This means 50%, then you repeat your move 100 times and you say see, the output is 53/100. Then you repeat and the output is 502/1000. So they start to get what 50% means. Then you do it with die and so on. However she has started it in wrong way. And I'm sure that most of the kinds do not know what 50% chance rain means.