Answer:
Assimilation.
Explanation:
Assimilation refers to the cognitive process that controls how we accept new information into account and integrates it into our existing knowledge base. It belonged to a portion of Jean Piaget's suggested adaptation procedure. The method is quite subjective as we prefer to adjust experiences or knowledge to suit our prior existing beliefs. As per the question, Millie is lumping a new animal into her existing knowledge base and thus an example of assimilation.