Divorce has become so easy and so common today that I'm afraid we've lost sight of just how terrible it can be. I've often said that a divorce is like a death -- the death of a marriage. Just as the death of a loved one brings us grief and loneliness and fear of the future, so can divorce. No wonder God has said that "He hates divorce" (Malachi 2:16, NKJV).
One of the most important things you can do right now is be her friend. That may sound trite, but it's still true. Often, we back away from situations that make us feel inadequate or uncomfortable, but we shouldn't, not if we want to help someone who's going through a hard time. Probably, the best thing you can do right now is to be a good listener, not trying to give your friend empty advice or quick solutions, but simply being with her. The Bible says, "My dear brothers and sisters, take note of this: Everyone should be quick to listen (and) slow to speak" (James 1:19).
Even more important, you can pray for your friend, asking God to help her through this difficult time and assure her of His love. God knows what she's going through; He also knows the feelings of failure or anger or fear she may be having. Most of all, urge her to turn to Christ and commit her life and her future into His hands. We're never alone when we know Christ.