The answer is: it reflects a gender difference between boys and girls during adolescence in traditional cultures.
Explanation:
Gender differences arise from the fact that women and men are not socialized in the same way in a society, meaning, being born man or woman will define multiple experiences throughout a person's life. Gender socialization begins at a very early age, which is why by the time the person is an adolescent there will be many evident gender differences, like the one mentioned in the question.
Based on the scenario, the method of reasoning that Bertha use is : Inductive Reasoning In inductive reasoning, a person will process multiple premises that all believed to be true and form specific conclusion from it