Hi Justalittlelost
and welcome to the family.
Yes it can really be overwhelming to suspect your mother may have a personality disorder.
It is little wonder you have many conflicting painful feelings.
I know I felt the same way the more I learned about my mother. Even now I struggle with guilt and disbelief as well as terrible disappointment at times.
As the others have said, there is a lot of information available and the resource library here is well researched and bound to be a help for you.
it is commendable that you want to help your sister - the best way for you to do this is to help yourself. the more you learn, the better equipped you will be to fully comprehend waht is going on and to make plans to cope. Then you will no doubt be able to support your sister.
I agree with both Harri and clljhns that if you can bring us more information, we can better tailor answers for you and send you in the right direction.
you may wish to review the material that explains exactly what BPD is.
here is a link to that:
bpdfamily.com about BPD (for Beginners)Ziggiddy