Every interaction with my 74 year old Narc Mom feels like she's competing with me. Why?

My Narc 74 year old mom gave me a ring she knows is too small for me deliberately. And I'm physically built small to start with. I left the ring on the table she would see. Today she asks me doesnt that ring fit you? I just told her it was too big. I wasn't giving her the satisfaction. She knowsI suffer from bulimia. She said something the other day that she might start going to the gym lol. She has never set foot in any gym. I'm the one that always has.

Why dos every conversation with her feel like ahe's in competition with me?