Anyone feel this way ?

My brothers half sister he just met keeps calling my unborn child hers to everyone and telling people that I'm "with child" Ive been keeping it a secret cause of past miscarriage and explained to her I don't like what she's doing but she continues. It's annoying and creepy to me and it's pissing me off to the point I want to flip out but don't out of respect.What should I do?