I have a hard time keeping my mouth shut, so hard to tell what I would say. I guess it depends on how well or if I even know the mother. If I know her closely, I would say, what the hell are you doing. If I didn't know the mother, I may just say something like "gee, I say katy today and her belly is pooching or maybe something like, I couldn't help but notice but looked like she had a scratch on her stomach. Heck, who knows..i know i couldn't keep my mouth shut about it. That's just me. But, I just thought of something. You could say, "I'm sorry, I know I don't know you, but you may want to know that other parents are saying something about Katy wearing short shirts at such a young age." Blame it on others, but don't mention any names, because it's actually coming from you and your mind, but you are also speaking for others that would love to say something. Just tell the mother you thought she should know what people are saying and as a mother yourself, you would want someone to tell you. If she doesn't give a crap, then I would lay it on thick.