Eddie one of the best ways to discover if she has intolerance, is by dropping stuff from her diet for a couple of weeks. If you think it's wheat, drop everything with wheat, it gives the body time to recover. Then reintroduce the wheat in small quantities. If symptoms re-occur you will have found your problem. Unfortunately, if it's not wheat and is something else in her diet, it could be a very long & laborious process trying to determine the source.
I'm lactose intolerant, but to date it hasn't caused me any problems with urinary infections, but we are all different.