Today, when my family was eating dinner, I went into my room to grab a cup I used for water. My mom had just gotten food for the week, and that is the time I always get my fill of milk or juice or whatever because my mom and sisters always drink straight out of the container and I am prone to get sick easily. So I went into my room to get my cup, and when I got it, I asked her if she had drank out of the container when I was in my room. She smiled nastily (from my perspective) and said "Yup!". I, and I admit, I was probably overreacting, yelled at her and told her that her drinking from the family container was disgusting because I get sick easily and that it was selfish and that she should not teach my younger sisters that's its ok to do the same.  AITA?