Need a sanity check

[ellie1234]

*edited to remove some detail*

My screwed up FOO has been a well mined topic of discussion with my therapist. But after a family get together yesterday I am again feeling completely bewildered by their behaviour and starting to doubt my sanity.

My old sister (BPD) lives with my enabling mother. There have been HUGE issues with my sister's behaviour since forever and my mother's response is to shame the person who has raised the behaviour as an issue and tell them they are the crazy one. To be fair, I think my mother is scared of my sister. I certainly am, as are my children.
My sister has no respect for any boundaries or rights of others.

Yesterday we had a birthday party for my daughter. My sister at one point disappeared upstairs and was, I thought, playing with our dog. My daughter told me afterwards that she was upset because my sister had gone through the bedrooms and helped herself to several of their belongings. My daughter says she happened to walk into the room while my sister had her arms full and she said "I'm taking these".
So I texted my mom today (I won't communicate directly with my sister due to her behaviour - I realize that's dysfunctional but I'm prioritizing my well-being). I was quite tentative, hoping to not end up on the shit list again because I have an issue with this.

My mom's response was to blame my daughter because if she hadn't wanted the items to be taken she should have protested (My daughter said, very correctly,  that she knew if she had protested she would have been screamed at and called names).

On an intellectual level I understand this is bizarre behaviour from my sister. I understand that taking someone else's belongings without permission is not socially acceptable (and is theft). I understand that expecting a child to tell an adult "no" is completely unreasonable. But I'm left feeling like I'm the crazy one who is overreacting.

I've already gone no contact with my younger sister (likely NPD but not diagnosed). I'd go no contact with this sister, too, but I would lose my mom in the process and I'm not quite ready for that.

Can anyone explain what causes those boundary violations in BPD? What is going through her head that makes this seem like reasonable behaviour?

[Penny Lane]

Hi and welcome! It really sounds like you've come to the right place.

I just want to affirm: You are NOT the crazy one here. It is totally inappropriate to go into someone's home and take their things (!) and then say it's their fault for not explicitly tell you that you can't take their things (!!!!!)

I would say that you are not overreacting at all. In fact, if it were me I would be giving serious thought to not letting your sister into your home anymore. That's how serious I would consider this. And I would also be giving some thought to whether she is a good person for your daughter to be around at all.

But I can't tell you why your sister would do something like that. My guess is it was something about her need for control.

In terms of dealing with it, though, I would check out the toolbox. It has really good strategies for maintaining a relationship with someone who shows these tendencies.

As you browse this site you might also check out the pd sibling and other family members board. I think you'll find a lot of people who understand what you're going through, can commiserate, and might have helpful suggestions for how to handle stuff like this.

I hope these resources can be helpful for you as you sort out what to do about your sister.