Hi MPG,
Welcome to the group

I'm sorry you and your parents are struggling with your sister's behaviors. Like
AmyBee said you are most definitely not alone. Everyone on this site has someone with BPD/BPD Traits in their life, we all "get it".
Can you expand on your story a bit? It sounds like your sister has been diagnosed. Has she or is she in Therapy? Has the rest of the family gone to Therapy for support at all?
What types of behaviors are you and your parents seeing most often? How is everyone reacting?
I hope to hear more of your story.
Panda39