Hi Mingyming!
I'm glad that you've reached out to our family here. There is a lot of helpful information to guide you in your new found discoveries about the possibility of your sister having BPD. Bi polar is definitely a diagnosis that often goes along with BPD. Are there any other behaviors that stand out in your sister which you think are of great concern?
I can understand your desire to try and let your sister know about her BPD, especially since her behavior is affecting those around her. I am curious as to your purpose in wishing for her to know. Is it because you wish for her to be aware of what she's doing so she will change and be nicer? With my uBPDm, I often wished for her to be aware of how much she was being hurtful, especially so she would change. However she never did. It's such a sad thing that BPDs are typically not willing to change.
It's wonderful that you are looking to educate yourself about BPD though.

What types of things have you learned so far that will help you in your interactions with her? I would like to direct you to the section on the right about BPD which is a great beginning place here. -------------->> >>
I look forward to hearing more of your thoughts!
Wools