Getting called fatty :-(

Brittany • Mommy to a wonderful 12yr old boy, 9yr old boy 7yr old girl 6yr old girl and 3yr old girl. Due March 11th 2023 with a boy.
I just seen my grandpas wife and she acknowledged me as " hey fatty" I kinda wanted to punch her in the face. I know I'm not fat, but the ignorance of people sucks. She's the 1st person to say anything negitive to me. Besides the "your small" and that's not a big deal.