I don't know Canadian law - only U.S. law - when it comes to suspected abuse. Medical and educational professionals are required by law to report suspected abuse. It is then up to the Department of Children and Families (or whatever that department is called in a given State) to investigate and determine the accuracy of the complaint. Jo has made a complaint to the police, as she told Robbie. Let's see what comes of that.
I totally understand Nicola's reaction: she doesn't want to see the family impacted by divorce. She, perhaps, is thinking of the financial consequences, but I'm sure there are mixed feelings regardless. She did state a fact to Robbie, and I don't think it was meant to hurt him as he took it: he doesn't have the history with the family that Daniel, Amy and she have. His history is one of non-acceptance by Don and mixed acceptance by Sue. Even though he was formally adopted, he is still not treated as an equal to the other children.
Dodger has done a wonderful job of presenting this story through Robbie's eyes. I certainly look forward to how things progress.