Hello there. My name isXXXXX and I am sorry to hear about Bella's skin issue. If this is truly Pemphigus Foliaceus (PF) then the treatment is modulating her immune system. PF is an autoimmune disease causing these changes in the skin. The scabbing, crusts, pustules, etc are all signs of this autoimmune disease. The most common drug we use first to try and modulate the immune system, to calm it down, is prednisolone. This can settle down the immune system enough to have the PF resolve. But it may come back with steroids alone so often time azathioprine (a different immune modulating drug) is comibined with steroids and then can be used long term to treat and control the PF.
So definitely try the round of prednisolone, she should be on it for at least 4 to 6 weeks most likely to see the most results. If this does not resolve it or if it reoccurs then talk to your vet about adding in azathioprine. I hope this helps. Please let me know if you have any additional questions or concerns. I would be happy to help. please do not forget to rate my response so I receive credit for my time. Thank you!