I would be tempted to respond in kind, say something like "I'm sorry you are having such negative things said about you at your work as a _________ (do you know what she does?) but you enjoy your work and she has no idea what your work trajectory is (presumably if you want to own your own daycare or something you would want X years experience, etc.) or anything about your personal life, hopes and dreams and you would appreciate she quit with the ignorant personal comments. Of course, the whole thing is made harder because you don't want to make her so angry or upset so she pulls her son out. . . You may just have to constantly/mildly reply something like, "Thank you, but I am happy with my life and plans for it" and turn away from her to someone else/change the subject.