Hi there,
Kudos to you for maintaining boundaries. I know it can be hard sometimes. You mention that your adult sibling lived with you, borrowed money and always played the victim. I bet you tried to help her out, to help her get on her feet again, right? But the thing is, with untreated BPD, her needs are endless, and furthermore, she's ungrateful and/or mean, and/or blaming YOU. It's like no good deed goes unpunished, right?
In my opinion, you are all adults now. You've done enough for your sibling. You know full well how toxic your sibling can be if you let her in too close. And your kids know it too. Sure, mom is "distraught" because she's spent a lifetime protecting/enabling/making excuses for her weakest child, and she just doesn't see how it's harmful to you. Maybe she can't be happy when her BPD daugter is clearly unhappy. But you know what? That's their problem. I think you stick to your boundary: everyone is an adult here, I'm staying out of it. I'm not meddling.
It sounds like your kids know better, too.
Here's an observation for you. In my family, grandma just doesn't seem to understand that 20-somethings are BUSY! Yet the reality for most young adults is that they just don't have the time, money or energy to be a caretaker of an aunt's emotional/financial/logistical/housing turmoil. In my opinion, young adults deserve to focus on forging their own lives. Maybe they show up to a Christmas or Thanksgiving gathering, and that would be wonderful, but demanding much more than that sounds too needy and whiny in my opinion. If grandma insists that the grandkids call their auntie regularly, check in on her and help her with domestic duties, I think that's out of line. Maybe you say something like, My kids are really busy these days, and I'm not meddling in their lives. Besides, Sis is an adult, she can take care of herself.
Now my guess is that your sis is needy, blame-y and complaining all the time to Mom about how horrible everyone is, especially you, for not being her emotional caretaker. You can't control that. Mom is falling for it. My opinion is that's between them, and it's probably best that you stay out of it. You can say that: This is between you and Sis, I'm staying out of it.
I know it's hard, but just remember, if you relax your boundary, things get infinitely harder, right? You deserve a peaceful life too, you know.


