My dad passed away and my uBPD sister is not handling it well

[earthbender]

My dad passed away in fall of 2019. He was struggling with post-op pneumonia after going through surgery to remove a tumor. He was on a ventilator for 3 months and during those months my mom and I basically lived in the ICU because I worked nearby the hospital so I would take the night shift and my mom would be there during the day. I am the youngest of 4 daughters but two daughters were unable to really be there that much (work, kids - literally no shade on them this is just the reality of what happened) they were still there a lot but in the beginning it was kinda just me and her. My other sister would come and go (she is the one with uBPD). She was okay during that time and after my dad died we all kinda thought maybe this would be her turning point. We were wrong. Now, over a year later she is back to her uBPD tendencies, abusing adderall, and being abusive to us. Over the summer she told me my dad would be disappointed in me (I know he wouldn't, him and I were absolute best friends and he was incredibly proud of me) and there are other examples that go on and on but I'm sure this community knows the kind of things that happen in these situations.

Anyway, getting to the point I guess, I don't know how to deal with my sister and my mom after a parent's death. Below are some of the things that have been coming up as we continue to deal with the aftermath of a passing.

There are items that belonged to my dad (jewelry, painting of him made by a friend, clothing) that my mom I guess wants us to have. She has been devastated by my dad's loss and is back to the toxic relationship she has with my sister because for the longest time her and my dad had a back and forth love her deny her love kinda thing (I'm assuming you guys all know what I mean by that), but my dad always said "it all comes back to love" so my mom has really taken that to heart. She also is just trying to give his things to us to have like physical reminders of him that we can have. I think it's great but my uBPD sister has a tendency to just take things and not tell anyone. Like in the past she somehow had two of my dad's rings that we thought were missing and voila she gave them to my mom one day. She can't see how we would be angry that she just randomly had two of his rings for YEARS and didn't say anything. She also has a camera of his that I guess she borrowed. Most recently she asked my mom for a beautiful painting of my dad that was hanging up. My oldest sister asked my mom to tell her whenever she was giving one of my dad's things away so that we knew where it was (I'd like to hear about what you guys think about that, it seems a bit controlling because she has gotten angry with me for having something of my dad's but I see where she's coming from because of my uBPD sister jus having things and never saying anything). My mom didn't tell us she was giving my uBPD sister the painting so when she sent in a picture to our group chat with it framed we were all like "wtf." My uBPD sister of course freaked out on us because we were upset and went on about how she has nothing of my dad's (not true, see above) and how it's always a problem when she gets something and brought up how other sisters have jackets and coats and whatever. I just wanted to put this here because it's an example of how the dynamic of my dad's things being distributed is going and my uBPD sister is handling it. I honestly don't even know if it makes sense but I needed to put it out there for some sort of support. I'm also living with my mom since COVID and I know firsthand how my dad's death has affected her. I know she doesn't want my uBPD sister to feel alone and sad (her and my dad barely had a relationship after all of the abuse she had towards him) but I just hate how she treats my mom and I hate how enabling and toxic my mom is with her. But I have tried to be both good cop and bad cop with my mom: trying to tell her not to give my uBPD sister gifts for Christmas, pay for her car, etc (the girl is 31 okay it's ridiculous) and also trying to tell her to get my sister into therapy (my sister refuses but I have no idea why because she also brings up her mental health whenever it's convenient in a fight) and other things to try and set up boundaries but to no avail. I'm not going to live at home for forever (honestly probably not even until next fall) and I'm honestly scared for my mom to be alone and have my sister come over and be abusive towards her (she doesn't have a job and will come over whenever she wants and take whatever she wants). Whenever she comes we are walking on eggshells around her because usually she is high on adderall. If we aren't giving her the attention she wants or we say something like "don't take the food out of the fridge and bring it home" she explodes. Last time she broke a lightbulb because my mom and I told her we weren't her Home Depot and she couldn't just come and take whatever she wanted. She exclaimed that this is her house and basically insinuated that with that she has the right to take whatever. She also always compares herself to us, her other sisters, and mentioned that another one of my sisters might take leftovers home with her.

Basically this is just a dump of some examples with the hope that someone can relate or has some advice. Really I just want my sister to be forced into therapy so that she can at least be diagnosed and we can have a starting point. Right now it's just like we're trying to stay afloat with no life preserver.

**Just a little more context I am 24 and my sisters are 34, 31, and 29. I have a close relationship with my sisters aged 34 and 29. I have never really had a close relationship with my uBPD sister because from my earliest days she has been abusive and even punched me in the face when I was 16, so that kinda ended things there for me. Since I have been getting older our relationship is okay- we chat sometimes and sometimes at family gatherings we will talk but I have never hungout with her alone like gone out for dinner or been to her apartment or anything like that. My other sisters have at least been with her alone and done activities.**

[khibomsis]

earthbender,   and welcome to the family! I feel terribly sad at what you are going through, mainly because it distracts attention from yourself, your grieving and making your peace with yourself with what has happened. I went through it a couple of years back when my dad died, and the only thing I can say is that it takes years and a lot of emotional work before you will feel better. Be patient with yourself.
The truth is, you cannot help your mom. This is her form of grieving and she has to work through it in her own time. The best you can do is try to set boundaries so that it affects you as little as possible.
I did not even think of getting anything of my dad's when he died. My uNBPD mom would never have allowed it. I had his love. That was enough for me.
Take care and keep posting, we are here for you to talk you through it.