In my opinion Margaret does not have to do anything because she was not in the conversation. If she inquires on the conversation, it could finish in a big problem. Margaret should respond until Marine complains about the incident. If Marine does, Margaret has to talk first with Sara and explain her that society changes through the time. Later she has to talk with the whole group about the incident in order to prevent another conflict. Because the expressions of Marie on the conversation, it seems that she has faced this problem before. I believed she would not affected because children of lesbian and gay parents are usually well prepared psychologically. According to the reading resources there is no evidence that parental sexual orientation
