worried sister --
I wanted to reply because it sounds like you and your sister are both going through a rough time right now! If she is dealing with a type of connective tissue disorder (RA, lupus, polymyositis, etc.), then her visit with the rheumatologist will be crucial. It can sometimes take quite a while to get a diagnosis if any of those things are the cause of other issues, but I'd imagine that they'll run a ton of bloodwork on her (key things to look for are any blood count abnormalities [white blood cells, red blood cells, platelets], ANA, rheumatoid factor, any specific antibodies they test for (this will depend on what they suspect initially), ESR, CRP...those are the main ones I can think of to start. The ANA will help rule certain things out if it is negative (for example, 95% of lupus patients have a positive ANA and most of the other 5% have other specific antibodies to help identify their diagnosis), but the ANA does not conclude that one has any specific disease or any disease AT ALL. Rheumatology can be a bit confusing.
I was diagnosed with lupus a few years ago after five years of trying to get a diagnosis. Fluid showing up on my x-rays, CT scans, and echos helped to push my diagnosis forward. I had one doctor say I had fibromyalgia (even though my muscles weren't even sore..) because my bloodwork was not overly conclusive. Later on, other doctors looked at the scans to see pericardial effusions, pleural effusions, and free fluid in the abdomen (all of these documented at different times). As one doctor told me -- fibromyalgia does NOT cause inflammation or fluid in the body, so that was not a sufficient explanation for the problems I was dealing with. If your sister has evidence of inflammation or fluid, I would make sure she is stern to push forward with a rheumatologist to find an explanation for such things. Fibromyalgia can certainly occur in addition to other disorders, but it does not cause inflammation (unlike things like RA, lupus, -myositis, etc.). Key info to know and understand..
Sorry for the long post. I know how hard this must be for you both because I have definitely been there. If she doesn't get answers from her doctors, she needs to not be afraid to MOVE ON and find new ones -- for many people, finding the right doctor to listen and pursue finding the cause of your symptoms (and not just placating you with drugs to treat the symptoms alone) will be the defining factor.
P.S. Regarding the white blood cell count, I'm not sure of what can cause a high WBC count outside of infections. Lupus causes my WBC count to be low rather than high, but that might be different in other disorders.