I believe that you raised an intelligent daughter who will eventually see through what her husband is doing. Your goal is to keep the lines of communication open so that you can be there when she needs you. It does sound like she will need you and I know that you want to be there for her when she does. For now you have to practice taking your mind off of what is happening to your daughter since you cannot fix it. I use my three mantras to help me whenever my mind tries to wander into what I now call "the abyss" which is a horrible spiraling trap that ends in utter despair. Oh yea, the mantras.......
1) What I focus on expands (so I try to think about something happy)
2) No news is good news (for when I don't hear from them)
3) Not my circus, not my monkeys (when I think they are making a mistake, I can't stop it so why do I worry about it?)
These three mantras have helped me avoid diving headlong into the abyss and over time I have learned how to keep away from those thoughts that suck my psyche into the darkness. It isn't easy when our children get older, strike out on their own and make mistakes. We, as parents, have to accept that we have finished our job and need to turn the teaching reins over to life. Our job as guides is over, now we are cheerleaders.
Hugs!!