Sherree, Sorry to hear about your friend. I am not a doctor, but have had crohn's for a very long time. Initially was diagnosed incorrectly. Since I have had several rectal fistuals, I suspect that your friend probably does have crohn's, not diverticulitis and she probably does have a r/v fistula. I have found out the hard way that taking your doctors word about your own body sometimes only gets you to a worse place. If I were her, I would insist that my doctor check for this, or get an appt. with an OBGYN and have everything checked out.
I am now with a very good GI doctor and my PCP is also wonderful, but, I still ask alot of questions. One of the questions my GI always asks when I'm in for a checkup is have you peed (sp?) air and that question alone makes me suspicious about your firends problem. I don't know wheter this helps at all, but I will hold your friend in my prayers. Let me know how things go.