Apologies for not using a better source than wikipedia, but I could believe that the anecdotal woman was not such an outlier, when you take into account that whole "one child policy" https://en.m.wikipedia.org/wiki/One-child_policy
I also discussed the indirect/cultural factor where one should learn about this. There are two complementary factors here: if the young woman was rural there was practically no way she never encountered a family with multiple children; if she was urban it was more likely she was educated and thus should at least learn about it from school and/or through literature.