How did this night turn into such a disaster?

So me, mom, and my little sis went shopping. We walk into the first store and my little sis won't stop asking my mom "When can we go! I'm bored! I hate this. You're mean." She was always shoving me and my mom, and stepping on our feet on purpose. So my mom kept on telling her to stop, and eventually got so mad that she yelled "I'M GOING TO YOU! STOP THAT! DO YOU WANT A IN THE MIDDLE OF THIS STORE!" She was really embaring me. Whatever. Then I went to the dressing room and tried on clothes. When i came out, my little sis said, "Mom went to the car." So i walk out to the car to look for my mom. Then my little sis says, "Just kidding. She's in the store". So we walk all the way back to the store. My mom is nowhere to be found. The salesgirl says "Look, are you buying this stuff you tried on or not??" I told her i wanted to buy it but i couldn't find my mom. So she says "What does she look like?" I start describing her. By now i was pretty annoyed. I said "Where is she? What the heck?" My mom emerges from the dressing room and gets FURIOUS at me for saying what the heck. I wasn't trying to be rude though, i was just confused, honestly! So then i show my mom a pair of jeans i want. She says "Aren't they too small??" And i said "No." She KEEPS asking me if they are too small, and i keep nicely explaining that they are fine. After the fifth time of explaining it, i start getting a little impatient. This makes my mom get FURIOUS again! She stormed out of the store without getting any of the stuff i tried on. So we went to Dillard's, American Eagle, and Belk with my mom pouting and fuming the whole time and my little sis shoving me and whispering mean taunts. On the way home in the car my mom goes on and on and on about what horrible brats my sister and I are, and how we ruined a perfectly good night and now she's not taking us to eat. I don't even know what I did to make her so mad, but how do you think this day went to horribly bad???