I probably wouldnt have said anything due to lack of confidence etc but one thing I do know is that that woman wouldnt have taken anything you said kindly. My guess is she would be the sort of woman who sees herself as bringing up her child how she wants, even if that involves a lack of care. By pointing out that what she did was infact wrong and not nice for the child, she will feel threatened. And anyone who talks to a young child like that can't be a nice person. Unless she was having a bad day, but I'm sure youd have seen the difference between a "bad day" and just being nasty.