I suspect she "misunderstood" the lesson intentionally (or was scripted to feign it) as a passive-aggressive subversion.
I don't know the girl, so I cannot say for certain it was intentional--but I tend to doubt that it was. I'm only a substitute teacher, but I have presented this lesson (without the statement about God). Students pick up on fact and opinions fairly easily, but I fielded questions on, "But what is an assertion?" I didn't explain assertion as a "myth", but myth could fit the definition. I said it was something that is stated and sounds as though it were true--and my synonym was "urban legend." (The students were excited to share a few of those.)
To me, it just sounds like a lesson that got out of hand. The one about God is hard. There are eye-witness accounts (Near Death Experience) and that can edge it towards fact, but not quite scientific fact (reproducible in lab conditions). Wish the mother and daughter could have simply talked with the teacher instead of heading for the school board.