Rant #2540

Upset with my younger sister about mother's day. My sister went out with her boyfriend and when he dropped her off at the house, she brought up plans to go hangout with his family because his grandma who lives out of state was in town. So her boyfriend wanted my sister to go to church with them and go out to eat afterwards. Which would've been fine if tomorrow wasn't mother's day. I could tell that it hurt my mom's feelings when my sister brought it up saying that she wanted to go over there. And it made me upset too. I didn't say anything because I didn't want to upset my mom even more, but I really came close to going off on my sister. Especially because my sister was really trying to fight my mom on the issue, which probably made my mom feel even worse. Even though my sister wouldn't be gone the whole day, I don't think it's fair for her to just ditch my mom for her boyfriend's family on mother's day. Idk am I wrong to feel this way?