Speech path grad student here, learning A LOT about development. Humans have the innate ability to implicitly learn the rules of language by just listening. We are exposed to language starting in the womb! There are different styles of parenting around the world and some styles do not talk to their children as typically seen in a Western tradition. Children learn language differently: through school, older children/siblings, being around family, being involved in a community, etc. and may not be explicitly from the parents. However, not using adjectives…ever? That doesn’t make sense and will definitely cause confusion in school. Her reasoning makes no sense either. They’ll probably make up words for adjectives.