I'm sorry to hear about the problems you are having. A month is a long time to be dealing with runny poops.
While Orijen is an excellent food it is also high in protein and since she hasn't been eating a lot of protein lately introducing it now may just aggravate the problem.
Have you tried the vet diet food? I know it isn't the best but it does do the job. Personally I would try that first and then switch her over very slowly once her problem is solved.
Has the vet tested again for Giardia?
Goldens are like potato chips, you can never have just one.