What to do?

I am so burden with the fact that there is a woman and child -so much like me and Chase who is being lied to in such HUGE way. I keep wondering where Chase and I would be right now if someone had only told us the truth and I feel responsible to be honest to her, and more importantly, as a mother feel for her child as I sit and watch mine suffer! I have no idea what she knows, -but I am SURE she does not know the truth. NO WOMAN would be ok with what her husband has been doing with me. Not only do I feel like she needs and deserves to know the truth, but I feel like I need to tell her how sorry I am. I KNOW that I didn't knowingly do anything wrong...... but my heart hurts for her and her future. To know that this "man" has done this to AT LEAST both of us is killing me! Both my son AND I know how good a liar and manipulator he is... and obviously he has had PLENTY of time to plan how he would spin this.... so I have NO disillusions that he will get her to believe him and not the truth.... but I feel responsible for letting her know what has happened....to give her and her child a chance to get away from this horrible person that everyone down there thinks "walks on water".... to let her at least have the truth so she can have her eyes open to what he is......I am just so burdened. Everyone tells me that not only will she never believe the truth ( trust me I am LIVING IT and I can't hardly believe it myself)-but that it is not my place to tell her, to close the door on this WHOLE HORRENDOUS MESS and move on with my life. But if I don't who will... if I don't speak up- I am as bad as the people in my life who knew the truth- but refused to be honest with me-because that was the easy way out..... is that the kind of person I want to be???? more importantly.... is that the kind of person that I can look at in the mirror and live with?????