Best friends can mean well but I hear so many examples of them actually causing more problems by trying to "help." Make sure your friend knows that from now on you're going to do you and she can support you by listening, no more.
As far as trying to undo the impact of the damage she has caused, you should leave the issue alone right now. Do not try to contact him, no matter how hard that may be. It seems stalker-like. Blocking literally means he doesn't want to communicate with you. Let some time go by and put it on your friend to connect with him in person, not via social media to explain. She should admit what she did, but I'm not sure it will make a difference.