Annoying sister in law

So I’ve already told my parents and my husbands parents that we are pregnant and we asked them all not to tell anyone until we are more around the 12 weeks. I’m a heavier set girl so it doesn’t show yet, but my sister in law keeps asking everyone, but us, if we are pregnant, she asked my MIL and said that I’m wearing a lot more stretchy type pants and look like I’m gaining weight. I don’t know if it’s my hormones or if I’m making too big of deal out of this situation, but it’s driving me crazy!!! Why can’t she butt the hell out and stop being so freaking nosy?! Like I’m too the point where the whole world will know before her family ever does. Any advice ladies?