My grandparent(s) were waiting to see the doctor, ...

My grandparent(s) were waiting to see the doctor, & me & my 12-year-old niece went in to use the restroom, & when we came out the woman at the front desk asked if we were patients, I said no, then she tells me that the restrooms are for patients only for future reference. Extremely rude. We did nothing wrong, & didn't bother anyone. There was NO reason for her to say that to us in front of everyone in the waiting room. She was very condescending. There's an addiction recovery place next door, so I guess she assumed that I was an addict & using their restroom wasn't allowed.