I am in a difficult situation and don't really know how to handle it?

My best friend broke up with her boyfriend a few months ago, because she doesn't love him anymore. They were together for four years. He messaged me today asking if we could meet up and talk about what is going on because he doesn't have anyone to talk too. He has suffered with depression in the past and I feel like I should meet him but obviously it is very strange because of my best friend, but I know that if I tell her I'm meeting him she will contact him and have an argument with him. I really don't know what to do? I want to be a good person and help someone, but I also don't want to hurt my friend.