How do you comfort someone?

I just got a call from my BFF about 5min. ago. Yesterday her grandma was admitted into the hospital for surgery. After they found an aneurism in her chest area they admitted her into ICU. This afternoon she went into a coma and stopped breathing for about 3-4min. before the doctors could stabilize her. She is still in a coma and I have no idea how to help my BFF! How do you help someone through something like this?