Am I overreacting?

Morgan
So we haven't told anyone yet that I am pregnant but once we do I am so scared that my husbands family especially his sister is going to tell everyone else before we even get the chance too. It's making me so mad thinking about it because she is so hateful and negative and any information she gets on anyone she tells the whole world like its her business. This is my first pregnant and I want to be the one to tell people but I know she will get to it before me even if I do ask her not to tell anyone and let us do it. I feel like I'm overreacting but then again it isn't her news to tell let alone her business, she isn't the one pregnant, I am! Anyone else have a similar situation?