I won't bore you with backstory. I really want a relationship with my BPD SIL, but it's SO HARD. She builds and breaks alliances within the family like it's fucking Game of Thrones. She hates you until she hates someone else and then she wants you take her side. She never. stops. talking. 

I'm hoping I can talk to others who might be able to help me understand what it's like to be my SIL. How can I be a sister to her?