Somebody please explain this to me?

Yesterday, my brother wanted "Alone time" so my mom told me I had to stay in my room all day, and I would get something. So, I agreed. Later, she asked me what I wanted, and I wanted my cousin to spend the night. She says no because she is a girl, and she doesn't always hang out with my brother. I said fine and went on with it. But, my brother asked if his friend Connor could come over, and she said yes. So today, I am trapped in my room again so they can hang out. Somebody please explain...