It sounds like you handled the external situation reasonably. The challenge is not personalizing her response, which could just as easily be embarrassment and worry - I'm sure she sees this in her daughter elsewhere - and not about you at all. You will definitely teach your son to be bullied if you teach him by your behavior that it's not okay if other people seem ruffled and that it's your job to smooth it over. If they don't plan play dates anymore, that frankly sounds like a win, unless you can give yourself permission to set boundaries on behalf of your son, whether or not other adults are present. If this friend is someone you especially enjoy, make grown-up plans at another time, with separate babysitters.