You could tell her as others have pointed out, this is a good EP to teach you how to deal with opposing forces. Whether you make Sims behave and be nice to others, this can also teach you about different personalities in the world. And what it means to offend them, what is considered rude and not rude and opens up a perspective of different hobbies meaning more to others than your Sim. And how to handle opposing views and or not handle them and what consequences being mean or rude to others gain actually do. This opens up many views of socialization on one hand and it can teach you something about different cultures and teach you how buildings are different in different parts of the world. Architecture is always good to learn and how something works. Though we can do a lot of silly building in these games, it can teach you how 3D games use those tools to bring to life what you imagine onto the screen and actually be workable.
The Sims is not only a social game but broadens your horizons on many different levels. Maybe if you are really good this year your mom will surprise you. But explain it's not just a silly game but offers you many insights into how 3D games are built and work even by just playing you somehow learn these things over time. And can broaden your interests in what you want to do in your life.
And that is all true.
