Dealing with a Histrionic Family Member

I have a sister who is a textbook Histrionic. All of my life (I'm 24 now and she's 28), I knew something was wrong, but I thought "she's just a shallow person." I finally figured out she has HPD and I was floored by how much she fits the criteria. The worst part is that no one in my family seems to see it. They are too concerned with their daughters fighting. Even therapists are wooed by her personality and cannot see what she is doing to herself and to her family. After years of trying to deal with her, I've given up. She started a heated argument over nothing (usual melodrama) and declared that I am dead to her. Even when I respectfully asked her to not get my parents involved, she insisted thus giving them extreme stress. My parents are pressuring me to "solve this" by flying to LA (where she lives) and seeing a therapist for 3 hours, as if that can solve it. Since my sister is the one who demanded I see her therapist, I chose not to give into her terrorism. Anyway, my question is, how do people deal with such "hardcore" histrionics? Is it best to just pretend I never had a sister? I've realized we can never be friends, so I tried to just be cordial, but even that wasn't good enough since she wanted more attention. Is it always all or nothing? And if somehow my parents coerce me into having a "relationship" with her, how do I deal with her?