And, think of this.... if you did take the crazy route of an anonymous tip it would still come out that you were condoning this behavior because her "books would be opened" and it would be visible that she was in fact doing this while living with you. It wasn't an issue to you then or not enough of an issue to report it but it is now?
So giving an anonymous tip really wouldn't do much good now would it? Either way the time lines will come out. Again, I think you need a better attny if he/she is feeding you all these ideas.