
Hi Gaby,
were it my dog I'd rather have a definite diagnosis of the problem than simply treat symptoms - some of which can be the same in a multitude of disorders that really require distinctly differing approaches and treatments.
You mention "irritable bowel disease" and also "inflamitory bowel disorder" - these are two very different problems with one being considerably more serious (and, if mis-diagnosed, potentially life threatening) than the other.
To clarify,
IBS, ie Irritable Bowel Syndrome, can quite easily be rectified by monitoring of diet - similar in method to humans suffering the pain, bloatedness, discomfort etc of IBS.
IBD, Inflammatory Bowel Disease, is a *significantly* more serious condition and IMO requires ongoing veterinary supervision as it is both a serious and incurable - although manageable - disease. Factual diagnosis of IBD necessitates biopsy, either by endoscopy or open surgery depending on the size of the dog.
In any event, in both of these instances, providing a high fat diet could prove detrimental and to that end I'd want to know exactly which - if either - of these complaints was being treated.
While many of us balk at the thought of using steroids, it is worth noting that some dogs gain a whole new quality of life by their usage and while this will hopefully not be the case (through need) for your daughter's dog, the use of them should not be written off lightly.
FWIW, personally I feed a primarily raw diet and agree that for my dogs it has been a fabulous switch and has helped me put a significant covering on a dog that was much too thin and reedy yet impossible to body-up on any commercial foods. That said, as with any diet, not all dogs will necessarily be the better for it. As this dog is apparently suffering from a GI condition or one which affects the GI tract and/or ogans, then messing around with a complex new feeding regime may be ill advised until the dog's medical condition has been established and symptoms stabilised.
As has been suggested previously, a second opinion or at the least further testing to rule out major problems and establish the accurate reasons for this dog's ill health, would IMO be the first port of call here.
best wishes, Teri