Funny you say that, my sister suffers from it, my girlfriends bro suffers from it, and my girlfriend (a doctor has written a research paper on the issue! At the points when I was actually listening to what she was saying, the following information filtered through to my thick skull.
Its a fairly common issue, often brought about due to high levels of stress. The reason there is no 'cure' is that there is no ascertainable reason as to why it occurs, and it will vary from person to person. It is very much the case sometimes that when Docs can't be bothered to do the leg work, they will tell someone they have IBS just so they don't have to keep seeing a patient who isn't getting better. (sad, but true) It is quite often the case that an idividual will simply be allergic to a simple foodstuff, and with a strict diet, they can get around their IBS.
I have been told lots of things can make it better, such as anything that will de-stress your missus. Herbal and peppermint tea works well, and like a mentioned, working out what agrees with her with regard to food is useful.
I'm no doctor here, so don't get me wrong but I have seen it, and it can be a really horrible thing for a person to go through, be there and be supportive of her (I'm sure you will be anyway) and she will appreciate it.
Also, one last thing, it can go away as easily as it starts, so even though there's no easy answer to fix it, it may just go away in its own time.
