Almost nothing is harder than being a single parent, and my heart goes out to your daughter and to all who find themselves in this situation. I hope churches will do more to reach out and welcome those who are single parents (both men and women).
It's not only hard physically and financially for your daughter, but emotionally, also, as she faces the trauma of divorce. All too often today we think divorce is a quick and easy solution to a difficult marriage, but it seldom is. The feelings of hurt, rejection and bitterness that often accompany divorce create wounds that may take years to heal -- if ever. No wonder God has said, "'The man who hates and divorces his wife... does violence to the one he should protect.' ... So be on your guard, and do not be unfaithful" (Malachi 2:16).
What can you do? Frankly, it may be difficult to bridge the gap between you and your daughter because of what you once did; perhaps others will learn from your experience. Do all you can, however, to let your daughter know you love her and want to help her. Don't bring up the past; you can't change it, and dredging up what you see as your daughter's mistakes will only cause more hurt.
In addition, suggest some practical ways you might help her -- keeping the children occasionally, doing her laundry, taking her a meal, etc. Pray for her, also, that she will turn to Christ and learn to give her burdens and cares to Him.