Rude woman

So I work retail and this older woman who was not in the healthiest state physically or mentally brought her granddaughter in to get some shoes. My co-worker is 7 months pregnant and I just found out I am 6w6d pregnant. So my baby bump isn't showing. This lady's granddaughter was thirsty so I told her where our water fountain was and the lady told her "don't drink the water everyone in here looks pregnant with their big old bellies". I personally am not duper skinny but I don't have a huge gut. The manager is tiny with no belly. My customer who is a frequent flyer spoke up and told the lady that she was rude and that you can't get pregnant from drinking water.  The lady didn't like that she was told something back.