What would you do if someone called you pregnant and you're not.

Ashley • I am currently in college majoring in web design
Hello everyone, so today at church someone that I knew put their hand on my stomach and she asked "when was I due?" I laughed it off. But maybe next I won't be laughing it off. How do I handle this next time. I only see her at church and we don't talk outside of church. I'm single and not trying to have a baby and yes I do have a stomach that isn't flat but to have someone once in a blue moon who are older than me how do I handle it the right way? Or is there a right way? Depending on who it is I will laugh it off or I just want to slap somebody.