I know that when Sydney was having tummy trouble and I had to take her into the vet, I had to give her some meds, I fasted her for 24 hours then gave her the vet canned gastro food. I only bought 2 cans which I think lasted for 2-3 days and then she slowly went back to rice and chicken then back to her kibble.
Usually as soon as my two get the runs, I have given them a dose of pepto and put them on the rice & chicken diet for a few days and it has always worked. It was just the once when Sydney was actually throwing up too that I had to take her into the vet to get the medication.
I wouldn't be against the vet food if it is temporary to help get her system back in order but I would definitely not keep her on it very long (since we all know the quality of it is pretty low). My dogs have been on Orijen 6 Fish for a long time now and have been doing great. I really like Orijen.