It’s not considered bullying. She didn’t refer to you as fat. And she apologized for calling that section offensive name.

Bullying would be if she called you fat and not stopping after you asked her to. Her thinking that she’s better than you or making fun of you is your perception. You can’t be written up for what someone assumes you might be thinking. Yes calling section big momma isn’t acceptable. But it cannot be grieved as personal bullying.

Your assumption that she thinks she’s better than you might be incorrect.

Years ago I was very long term sick and due to that unable to eat, I lost a ton of weight and was barely getting through the day. It would be horrid to assume I thought I was better than anyone because I was skinny. I wished I was heavy, that would be a significant sign that I could eat. My aunt has incurable cancer. She’s thin like a stick.

You don’t know why she is thin or what she thinks. Don’t assume things about people. She made a mistake and apologized. Why such hatred towards strangers. Only after a few days on the job.