How to help Your Teenage Daughter with Boyfriend Troubles

My daughter is 16 and been dating the same boy for over a year now, and he had broken up with her, I am have trouble helping her, it seems I am saying the wrong things. Hopefully this is where I can get advice and it can be passed on to other parents for future reference. I thank you in advance. I have three older sons and this problem is not an nor has been an issue.