Your friend isn't entirely crazy. There are dozens of questions on the site like How can I reproduce the camera-internal postprocessing?, because it's completely true that the RAW processor in-camera is different software from desktop RAW software, and without intimate knowledge of both, it can be hard to reproduce the camera software's "look" with other software. So, if your friend really likes what the camera does, preferring the JPEG results is understandable. (See also Can in-camera JPEG have image quality advantages over (third party software) converted RAW?).
That said, the advantages of RAW are particularly high in this sort of situation, where you can't get a "do over" if you had the processing settings wrong. See Good examples of RAW's advantages over JPEG? and Why can I adjust the white balance of a RAW file but not a JPEG file?. (Also What are the pros and cons when shooting in raw vs JPEG?, but that's a kind of early question on the site, and as of this writing doesn't necessarily shine with great answers.) In short, if you take a perfect picture of the bride's expression but the white balance is off, you'll be glad to have RAW files. Or even if the exposure is really wrong, RAW will give you a better chance to try and salvage the image.
So, if your camera can shoot RAW without becoming unresponsive due to dealing with the larger files, and you have enough memory cards (bring extra!), you probably should go that way.
Some cameras (including, I believe, yours) have the ability to save in RAW+JPEG. This gives you the best of both worlds: you get the instant, in-camera results, and you also get the opportunity to change your mind. That takes even more space but is probably worth it.
Additionally (or alternately), some cameras let you post-process RAW in camera after the fact, which lets you use that engine to get the same colors and processing the camera would normally produce in JPEG, but with the chance to do it over. The downside is that you have to work on a tiny screen and the options will be far restricted, but many people underestimate the power of this. I use this 90% of the time now, and then I also have the RAW files if I really want to do something more sophisticated later.