adult sibling with undiagnosed BPD

Hi,

I'm really struggling with my 44 year old sister who has what I suspect is BPD. Everything I have read online and in forums leads to this diagnosis. She has suffered depression for years, and anxiety. She feels she is the victim and that lots of bad things have happened to her that are out of her control. She lies, is narcarsistic and talks about suicide regularly. She has been on a series of medication for years and is always in and out of therapy. The worst thing is that she still lives with my parents who are in their 70s. They cook and clean for her as she is 'too sick' to do anything. They give her free rent. But then she regularly abuses them emotionally. SHe has no friends left. Just our parents. I feel like I've not only lost a sister but also my parents as they are all consumed with her. I'm worried about what will happen when my parents aren't around anymore. They talk about buying her a house to set her up but it won't be enough as she doesn't cook or clean or work. My parents should be enjoying their retirement by now, not looking after an adult who is more capable than she lets on. She has them wrapped around her little finger and they are scared to leave her alone for too long so it's hard for them to go away.

My parents get very defensive when I speak negatively of her and ask 'how would I like it if that was my child?'. I really don't know how to answer that but I can't see my kids ending up like her. She needs some tough love but they constantly enable her behaviour. I made a decision to take a break from her a few months ago but I still hear about her all the time and my parents constantly give me the guilts for not seeing her. She is so toxic and bad for my own mental health but that doesn't seem to be as important as supporting my sister.

I'm at my wits end and can't even visit my parents anymore as she lives there.

There's more to the story but that's the jist of it.

Anyone else dealing with an older adult in this way?