Is anyone else surprised that this therapist never told authorities? Depending on how long ago this occurred, they are bound by law to contact them when they hear about these things. In situations like this, sometimes it's hard for females to come out and actually go to the police about these things, because a lot of times they blame themselves for what happened. The smart thing to do would be for her to file a report on it but evidence would be gone and it would be her word against his which a lot of times is enough, but she would have to relive the event all over again multiple times so it's rare for people to come forward about these things.
That being said, it doesn't mean it's ok for you to take things in your own hands. I know you want to hurt him for what he did and to somehow get justice for her, but like Vash said, you won't be any good to her in jail. The best bet is to be there for her and support her and help her through all this the best you can.
If you can't handle the thorns, don't crave the rose!!