SPM...You asked: "Why can't you? What is preventing you from telling her this?"
I did lightly try already once...thought I made a point, and then she said something later that made me sure she had not gotten the point.
I will have another opportunity coming up soon, as they plan to get married and I know she will be willing to listen to some good old advice - especially from me, being that I am divorced from her father...she is marrying a man quite like her father, and she will want to know what is ahead for her.
But this will have to wait another 6 months at least.
I don't know if you have grown children or not, but it is very difficult to tell them "don't do as I did" especially when they are happy and well adjusted, and when they have no idea how deeply you regret some of your own choices. In order to have fuller, more honest conversations with her about this, I would have to drag her father's image through the mud and I am not willing to do that.
However...as I said...as she approaches her own wedding, there will be an opportunity for me to tell her more. I may have to find a "dangers of a child centered marriage" type of book for her and preface my advice armed with marriage and relationship professionals who do not advocate putting your children between you and your spouse.
So my opportunity has not come just yet...I am biding my time until then.
