Broken-hearted

I found out this week that a very dear friend of mine is getting ready to go through a divorce. She has been with this man since high school (10 years), and they were great together. 
She hasn't said what happened, and I honestly don't think I want to know. He is a great guy and she is a great girl, and I don't want to think of either of them doing something to hurt the other. All I know is, it had to be bad for it to come to this. Neither of them went into the marriage lightly. And they neither one ever agreed with divorce. 
I had no clue things were going south with them, but in hind sight...I should have known. I should have suspected something wasn't right. I feel like I have completely let her down. It breaks my heart to see her go through this, especially since they were so happy together. I know all I can do is be there for her, but I wish I could do more.