Stepdaughter making fat jokes about me.

My stepdaughter is 12 and a half. She had started making fat jokes at me recently. She's poked my stomach and called me pudgy. And tonight she came up and asked me when the baby was due.. she knows I struggle with my body image.. her and I get along great otherwise, but I can't just brush off the fat comments..

I'm not proud of my body, but it's been so difficult for me to lose weight. She's a twig, just like I was as a teenager and has no idea how it feels to be unhappy about your body.