I answered in another thread, but yes, I have the antibodies. I am only treating with daily aspirin for now since I have not had any clots. According to research, 33% of people with ITP also have APS, so I'm surprised there are not more of us here. I wonder if that is because so few people are really tested. I have been tested several times and sometimes I have the antibodies and sometimes I don't - they come and go. I practically had to beg to be tested initially. My hemo turned me down several times because he said my counts 'went too low to have APS'. Wrong! Finally, my Rheumatologist agreed to do it. I had the antibodies.
Were you also tested for Anticardiolipin and Glycoprotein? Those two are also APS antibodies as well as the VDRL.
I'm sorry that your sister is on blood thinners. That can be a difficult thing to manage.