Being labelled anorexic 😒

Cee 🌟
My step sister (age 16, like me) has realised that I don't eat much and knows that itS because my anxiety makes me feel sick all the time however i do eat just not a lot at once. More little and often. Anyway she keeps saying 'oh you're like anorexic stop being stupid and eat' 
Or she'll say to my mum 'your daughter is like anorexic sort her out' 
Sometimes it's in front of my friends and it's makes me feel embarrassed
Even yesturday she said to me (because I couldn't finish a kids portion of fish and chips) 'your boyfriend is gonna be like ewww and run away when you become all skin and bone' 
I'm just so sick of these comments. It's really tiring me out. Please can someone give me some advice or at least say I am justified in feeling offended and upset by it.Â