Was I wrong?

I was at the Wic office today and you have to bring your child. So I brought my 7 month old in. There was a little girl about 5 and she was excited to see a baby. She came over and was talking to my boy. It was cute, she touched his toes his hand but then kept touching his face. I didn't know if she was sick but looked like maybe she Was? I said "We don't touch faces, but thank you!" In like a kind but redirecting tone. Her mother rolled her eyes at me and called her daughter away. I'm a first time mom and I feel kinda embarssed. I didn't want the little girl to go away as they where having fun playing, I just didn't want her to touch his mouth? What could I have done better ya think? I Also don't want to upset other people's parents. 😔