I'm 43, have crohn's, and have been in remission, symptom free for 20 years.
20 years ago, I was hospitalized for 2 weeks with a terrible crohn's flair. They wanted to operate, and chop out several chunks of my intestines. I declined, and wanted to exhaust all other possibilities before resorting to surgery.
I saw another GI doc who told me of some cutting edge research that showed that folks with acute crohn's flairs do better on an 'elemental diet'. At the time, it was basically a liquid, gluten free, dairy free diet, easy to digest meal replacement.
Since nothing was working, I gave it a try, and after a few months, was able to quiet things down within a few months.
At the time (20 years ago), I read everything I could about supplements to support crohn's. I took lots of fish oil, l-glutamine powder, and Pentasa (a prescription crohn's maintenance drug).
I remained fine, without any additional flair ups, while on this approach.
Two years ago, I decided to stop taking the prescription Pentasa. I was very nervous doing so, but I remained symptom free.
Three months ago, I discovered Paleo.
If 20 years ago I knew then what I know now, I would have been on Paleo for the last 20 years.
BTW, I have also ready many folks with Crohn's doing well on the Specific Carbohydrate diet (book= Breaking the vicious cycle).
Over the years, I remain shocked when doctors say diet has nothing to do with Crohn's.
I would encourage your friend to give serious attention to diet, read The Paleo Solution Diet by Robb Wolf (it's a fun read and spells out the Paleo stuff very well).
Best of luck,