Not sure if I'm way off the mark, but have you pressed charges against your mother for this (or other) incidents? If not, wouldn't your T be legally obligated to report this? Especially if she has listened to it herself (as opposed to it being hear-say).

I'm so sorry that this has happened to you, but I would just make sure you check what T's in your area are legally required to report. In my location, this is one of the areas where T's ARE allowed to break confidentiality and are mandated to report.