Frustrated

Chicks

We will not be finding out the gender of our little one until April, but me and my husband have made it clear that we really don't have a preference with this being our first. However, I get so frustrated when people already call my baby a "her." (Not because we don't want a little girl because we would love a little girl), but because people say "oh I KNOW it's a little girl." I just want to ask, "how do you know??" If they're right, that's great, but what if it's a boy? Will they be disappointed or something? Has anyone else experienced this?