I agree that you need to get a full, routine blood-panel done on your Love Bird, and make sure that you request that they add the PBFD test to the routine blood-work panel, as it's not part of it. The reason you want to get an entire routine blood-panel done is because #1) They are going to have to take blood to do the PBFD test anyway, and #2) This way you'll also be able to rule-out things like an infection, liver disease, kidney disease, etc. It will also show if it's related to malnutrition or a deficiency of some kind. So you can find all of that out at one time if you get the full blood-panel done and add the PBFD test to it...
It is odd the way the feather loss is only on one side and not the other, typically they molt bi-laterally, but the one good thing I can see from the photo is that she does already have some pin-feathers growing back in in the bald area, so that means that she is growing some feathers back already. So this is a good thing...
Try not to stress-out, I know it's hard but your bird can sense that you're stressed, and then that stresses her out too...PBFD is always something that needs to be checked for any time there is a feather issue of any kind, but it's not the most-common reason of issues like this at all. It could be something as simple as a Fungal/Yeast or Bacterial Infection, or some type of parasite. So no need to rush to the absolutely worst-case scenario just yet at all...Many possibilities here...And if her only symptom is the feather loss and she's not acting sick otherwise, like she's not sleeping more than usual, she's not lethargic, she's not vomiting, has no runny/watery droppings, isn't coughing or wheezing, and is still eating normally, then that's good too...
If you need help finding the closest Certified Avian Vet to you we can help you with that too...You don't want to take a bird with a potential serious issue to an Exotics Vet, you need to find a CAV or Avian Specialist for this...