Hi Nyena,
This sounds like a really rough patch you've gone through, and are still going through. You've come to a really good supportive place. There are people here with varying levels of knowledge and experience, but we all share one thing in common, and that's a pwBPD, and we are all supportive of each other. It sounds like your mom is in a super precarious mental health state. That of course is affecting the rest of you in the family. I'm glad you've found us.
Your experience is quite different than mine has been, so I feel limited in what I can offer. My mom had one patch where she was talking about suicide, but she never had a plan, so I have no experience with actual suicide attempts from my mom.
It sounds like you have an aunt who has a grasp of the situation if she brought you a copy of Stop Walking on Eggshells. That's good. At least there's one family member who "gets it". Is she your mom's sister, or sister-in-law?
It sounds like you live with your mom. Is that correct?
Does your mom have a family doctor? Is s/he aware of what is happening with your mom, and how this is affecting the rest of the family? I ask, because when my mom was going off the deep end, I made an appointment to go visit my mom's doctor to tell him what was happening. Because of doctor/patient confidentiality, I knew he probably wouldn't be able to discuss my mom with me, but he listened very attentively, and I believe I "connected a lot of dots" for him. He was very sympathetic, and gave me extremely good advice. The appointment turned out to be more about my well-being than my mom's, but at that point the well-being of both of us was wrapped up together. Is visiting either your, or your mom's family doctor, something you could try, if you haven't already done this?
Have you ever seen a counsellor or therapist?
There are also suicide hot lines you could call for expert advice, if you are concerned about her well-being. And of course, if you believe she is in imminent danger because of possible suicide attempt, call the ambulance (again).
You mention she recently survived her second suicide attempt. Do you know if there was any kind of "after care plan" for her when she was released from hospital?
Have you already found the resources and info on this site? Here's one on suicide, just in case you haven't...
https://bpdfamily.com/message_board/index.php?topic=69192.0Hopefully other's here with more experience around suicidal pwBPD see your post.
Let us know how we can be most helpful.