I just got a call from the vet's office (well, I didn't just get the call, because I made a few phone calls after that), and they told me that the FeLV test came back absolutely, positively negative.
Evidently, the anemia is not non-regenerative. She's trying very hard to make red blood cells, but her immune system is just going crazy attacking them, so the bloodwork looked non-regenerative, if that makes sense. I believe he said "hemolytic anemia," but cannot recall off the top of my head. He's stopping the doxycycline, and wants to increase her prednisone dosage, and he's putting her on another immune-suppressing med -- a steroid (the name of which escapes me at the moment -- basically it's something they give to organ transplant patients to suppress the immune system so it doesn't attack the new organ).
And here's the really good news: I asked the vet if this was something she was going to have to live with for the rest of her life, or if this was something she could theoretically recover from. He said that he didn't want to make any promises, but that it was definitely within the realm of possibility that Bronte could make a full recovery, and eventually go off the meds.
If you'll excuse me, I'm going to go hug my kitty now.