I and SIL are part of a large private group on Facebook, thousands of people. A lot go anon and post questions similar to here. AIBU to be raging that she has posted a reply to a member giving advice and adding unkind things about my DB and my nephew? They are recently separated after a short marriage. My DBs mental health is fragile atm and I’m torn between what to do. I’m worried in case someone else tells him about it and I’m worried about her reaction if I call her out.