My (28M) sister (32F) is more depressed and lost than I have ever seen her, and most of our family has given up on her. Please help me figure out how to navigate this.

Hello, this may be long and I am unsure how to structure this post, but I need to get these thoughts out and get some advice from some well meaning redditors on what to do next.

To start, there are 3 siblings in my family. Me (28M), my middle sister who we will call Jane (32F), and my eldest sister who we will call Alice (35F).

Since she was 15 and I was 12, Jane has always been the tough one to get along with in my family. When we were kids she fought with my parents viciously, often in mean spirited and cruel ways. Her and my dad fought like animals, frequently getting physical, and almost resulting in my parents divorce many times. She would say low blow things to him - insulting him for not going to college and working as a FedEx delivery driver, calling him a loser, etc. My sister had a really mean streak growing up, starting with internet bullying of another girl at her school. That is not to say my dad is innocent in all this, my dad handled things with her wrong every step of the way - but truly understand - it was very hard to live with my sister. She could be quite cruel.

After years of these issues, my parents finally forced her to see a therapist, who told her/us she had Bipolar disorder. Jane refused to accept this and didn't like the way her medications made her feel, and would hide them. Ultimately, she never stuck with any treatment programs or therapy and my parents weren't strong enough to force her.

Because of the extra treatment Jane got due to being such a handful to deal with, my eldest sister and I often got the short end of the stick. This never really bothered me - I was/am a well adjusted kid/person who for the most part don't blame my parents for a bad childhood. I have no complaints.

My sister however is a different story. She shared a room with Jane and Jane would fight with her boyfriend over the phone, screaming at the top of her lungs, she was inconsiderate, she was hard to live with - and ultimately Alice was booted from her place in the room. Not officially, but my parents wouldn't step up to put Jane in her place the way she needed to be. Ultimately, Alice ended up moving out to live with our aunt and uncle, and never moved back home.

Since then, Alice has held various forms of resentment over the years against Jane. It's important to understand that Alice is a very mean spirited, and cold person. She lacks compassion, holds grudges, and can be quite negative. Jane wasn't perfect and made many mistakes, but Alice never wanted to see past the drama and old wounds she had suffered at Jane's hands. Every little thing Jane did that didn't really bother the rest of us - Alice seethed over.

To Jane's credit - she is not the mean spirited, cruel person she used to be. Her and I have a good relationship, and despite her being a mess, we care a lot for each other and she is a kind person with a lot of problems she refuses to accept. We all believe in our hearts she is in fact bipolar - we've seen it in behaviors of hers, but still she will not accept it. Insisting that she has OCD, anxiety, and ADHD.

Fast forward to 2020, Alice decides after speaking with her therapist that Jane is toxic, and she doesn't want her around anymore - and that includes no coming to her house on christmas. We organized a separate Christmas event with Jane, which Alice seethed over. She saw it as her and her daughters (my nieces) getting the short end of the stick. It feels in a lot of ways, like Alice wants to be the only sister from now on.

We got through Christmas doing the separate Christmas thing, but it obviously stung when Jane finally found out Alice just didn't want her around.

Fast forward to March/April, my birthday comes around and Jane was seemingly in the midst of a manic episode, and was acting highly erratic. I am ashamed to say that I went no contact with her for a little while because I simply didn't have the mental space to deal with how she was being.

A month later, her best friend passes from overdose. I still didn't reach out to my sister to talk to her and again, I am ashamed. After that, my sister wasn't the same. Nobody heard from her for months. All we would hear is the occasional text/email from a third party looking for rent she skipped out on or whatever else. My father became close with her, as the only person who she would really talk to. I believe he has a lot of remorse for how things were in her teen years.

My sister finally surfaced for real a few weeks ago, and she is highly depressed and in a more broken state than i've ever seen her. She told my dad she wants to die, she feels empty and alone, and like she has no one. She says she is embarassed and has become highly anxious, she barely leaves her house (when she used to be a huge party animal who loved to go out) and is scared of everything. My dad went to see her two weeks ago, and they had a good visit. I had hoped things were getting better, but they weren't. Jane continued to not answer calls or texts (at this point I am back in her life, we have made peace with my behavior towards her and I just want to help her be okay.)

Last night, she sent me 20 minutes worth of voice journals of her in tears, talking about how grateful she will be when shes past this, how she hates the way she feels, how she misses all of us, even my sister. I have never heard her more broken, and it tore at my heart. She is really really really genuinely hurting. She specifically said she wanted to talk to my mom. We talked for a long time, and she says she understands that shes not mentally well, and that she needs help.

My mom is another matter entirely, Jane has done a lot of really shitty things to my mom (and to my parents) over the years in her mania, and my mom is done with her. My mom loves her, but my mom has a perpetual victim complex where she says "I'm 60. We've been doing this since she was 15. Your father can handle her. I can't do this anymore. She needs to get help before we can talk"

So here is where we are now. My eldest sister still will not allow her at Christmas and said "if she gets help, I will be willing to mend fences". My mom has seemingly given up on her unless she gets help. And my dad cares deeply, but he is old school and an inch deep emotionally. All he can do is be there for her and tell her she needs to see a doctor.

What can I do for my sister? I am going to see her this weekend - and I told her I am spending christmas with her the rest of the family be damned. But I can't force her to see a doctor. She says she understands she needs it - but she hasn't acted on it - and it feels like our families lack of support is causing further damage.

tl;dr my sister is lost and more depressed than she has ever been and everyone has given up on her. She is definitely bipolar but is dragging her feet on getting help.