Random 3 year old girl kept kissing my son today....

So we went to the mall and they have this soft playground area and this 2.5 or 3 year old girl kept saying he's so cute and being really playful and kept kissing his head, she was a super adorable kid but I felt so uneasy and confused how to handle the situation... her mom kept saying no don't do that but she was busy with her 8 month old. How would you handle this situation??! She did it at least 5 times and it's a small play area so even when we moved places she still came right over to us.