Girls are supposed to get married and care for the family - this was the view at the time. So they learn a lot of house economics, handiwork possibly even an instrument or foreign languages. Mathematics, physics, chemistry and biology are thought of as very "unwomanly". Girls don't have to know such things, people thought.
A few girls do not keep with this way of thinking and study these subjects anyway. This also includes the woman that Albert Einstein later marries.