Zari has had a set back...

Has anyone dealt with Ehrlichiosis ? Zari was treated for 20 days with doxycycline..she did require one IV for dehyration and received a vitamin infusion...she seemed to be responding, her appetite improved a bit but now into the second week post antibiotic completion she is not eating, is dehydrated, no energy..nauseated..she is turning prematurely gray and looks much older than her 5 yrs....we took her back into the vets today and she was started on an IV for dehydration..given an injection for her liver...and two immune system boosters in her IV...she now has to go back every 3 days for an injection.....the vet said her immune system has been compromised by the Ehrlichiosis...any suggestions would be much appreciated...I have never dealt with anything like this before .