I think it is great you talked to your D about this. However it appears to me that she is still holding out hope that you and your STBXW might reconcile -- and she may think she can affect that outcome or even that it is her responsibility. That will only end up hurting her, and it is a mistaken notion all too common to children suffering from S and D. But we parents need to do our best to assure our children it is neither in their power nor in their responsibility to try to repair the R. (Heck, if the LBS is certainly in a poor position to change things, the children definitely are.)
While the collateral damage from D is such a destructive consequence in the lives of these innocent ones, we can instruct them that there are indeed things in life to which we just do not have any control. It is a painful lesson to learn and a costly one in these circumstances, indeed, but the sooner we do learn the better.
Once D8 understands that she is fully absolved of any responsibility for her parents' M, whether success or failure, I am certain she will be more at ease. I am not saying the pain of seeing one's parents split apart will easily go away, but her own sense of guilt and helplessness will be put in better perspective and allow her to cope with it better.
