I'd love to be of any help but it's hard when I don't know much about the dog & the history.
What type of infection?
How long has the dog had this illness?
What meds have been used in the past? Pred is a steroid not an antibiotic, and while it may help with other problems the dog is having it will not help with the actual infection.
Has she seen any specialists? Or even a second opinion?
Has the dog had any tests done, like fecals & blood work?
What type of food is the dog eating? How often & how much?


I wish your friend the best of luck.