Does she have any lupus symptoms? Has she been tested for lupus-specific antibodies like anti-double stranded DNA?
A positive ANA is not entirely unusual, and not at all specific for lupus. While most lupus patients have an elevated ANA at some point (mine has been 1:2560), lots of people can have elevated ANA without ever developing autoimmune diseases.
Here's a link to the current diagnostic criteria for lupus:
en.wikipedia.org/wiki/Systemic_lupus_erythematosus#Diagnostic_criteria
I have lupus and ITP, and when I dropped below 30mgs of prednisone, my platelets drop. I am also on Plaquenil. I am being treated with Rituximab (Rituxan) right now, to try to elevate my platelet count.
I hope this helps! Any more questions?