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Well, this has been going on for around 2 years or so, my sisters rages and anger. She slams the door so hard that me and my family's heart jump out. I was always the one to comfort her and rescue her from her pain until this year, I am burnt out, all that hurt had finally caught up with me and I felt powerless. All I tried to do was help her and listen to her. Now that I am taking care of myself, she rages about me (it used to be my dad). I have no choice but to take care of myself and my feelings, and walk away (not literally, since we live in the same house) but we don't speak or see each other. I feel fed up and just want it to stop, my poor mom is having a hard time and so are my dad and sister. I want to help her but I find it hard to, because when I did, I began to sink with her. I sometimes feel anger that she cannot take care of herself and see how damaging her behavior is, I sometimes feel like I am the older sibling and not her.

You can't rescue her from her pain.  This may sound harsh, and difficult to accept. But she has to find her own ways, perhaps with supports (parent, family, Dr, T, friends), but rescuing is not support.  Does that make sense?  There are much better ways to support.  Have you had a chance to read some of the resources on this site?  SET?  Validating questions?  Not JADEing? Boundaries?

The harder I tried to help my mom, the worse she treated me.  Could this describe your situation?

Her problems are hers to solve right?  We all learn lessons best when we learn them the hard way and under our own steam.  Then we also get the satisfaction of solving it on our own.  Then we aren't forever "in debt" to the people who rescue us.  Also, my uBPD mom resents every suggestion I have.
 If I say white, she's gonna do black.  If I say black, she's gonna do white.  So I finally figured out it's not my place to say.  Instead, I can ask her "what do you think?"  Ask the right questions (without any emotion) to guide her to solving her own problem.  pwBPD are way more emotional about their problems than the rest of us.  They feel them with 10x more intensity than us non's.  It's hard to watch.  So if it's too hard (especially if you are the target of her fears/frustrations), leave, which is what you are doing already.  

Yes.  Great strategy.  Boundaries are necessary and healthy.

Are you familiar with I statements?  You could use an I statement to communicate a boundary.  This will give her a chance to sit with a problem and work it out, because an I statement also communicates what you want.  
eg: I feel _______ when you _________.  Please _________ (state your need clearly eg. Please don't yell at me.) It may take longer than you like for I statements to start having the desired effect.  I statements will work best when she is not too emotional.  The more emotional she is, the less she will be able to hear or process anything you are saying.  That is the time to quietly exit to the washroom.