I have a friend that will still show up to playdates and toddler classes etc when her son is ill. I've voiced many times before that I wouldn't take my son anywhere whilst he was ill so he wouldn't get the other children ill. She has openly agreed with me that it's the right thing to do.. but the last few times my son has caught something, its been from her son as she has not given the same courtesy. Her son was diagnosed with tonsillitis the day before yesterday and she has just confirmed in a group chat she will be coming to a birthday party tomorrow. How do I, and should I even talk to her about the true reason I will not be attending the party tomorrow?