I was once accused of not taking action for a mom who thought her daughter was being bullied in my home. Instead of accusing blindly, I sought out to know what had happened, giving a fair chance (to whom she accused) to tell their side of the story. It turned out to be a miscommunication. By the time I wanted to clear the air, I was suddenly accused by the mom of being not a good friend, apparently because I supported the bully.
But when I tried to understand what she meant, I googled what bullying can actually mean and this is what I found: