Looking for relationship advice?

I'm new on here.
I haven't been on a forum since I was like, 13 aha, but I'm really lost.

Uh, I met my girlfriend when we were 13 actually. She was struggling with SI and depression at the time, and when we dated the first time when we were 14 we were very codependent. It was really unhealthy.
One day in November 2009 right before our one year she was hospitalized. Her parents cut me off from her so we could learn independence I guess(I totally respect their decision and being 18 now I'm so thankful for that) I told them about her self destructive behaviour and she was mad at me for that. We didn't speak for 3 years.

I never stopped thinking about her and prayed for her health and lit candles every once in awhile but got myself into therapy and I'm doing awesome. I'm really independent and happy.

We started talking again last April and We've been dating again since this past New Years Eve.

She goes to therapeutic boarding school and at first I thought she was doing AWESOME. That's what she made it sound like.

I mean for her I guess it's awesome and she has definitely made progress but I guess in the time we didn't speak she got A LOT worse.

Anyways it's been over 5 months and she's just been up and down and up and down. She's 17 now so there's no official diagnosis but I'm just looking for advice on how to support her the best that I can.

I get to see her maybe every few weeks because her schools in another state.
I'm going to be getting my license and my apartment and moving out to be a grown up soon and she's sort of behind. Her priorities involve recovery, not the same list as me.

She's on anti psychotics and anti anxiety medication and those help, but sometimes she gets horrible intrusive thoughts about SI and homicide and suicide.

She receives therapy 4 times a week at this school and is getting all the help she can get.

I just want to be a good boyfriend.

I took a psychology class my Junior year and that knowledge helped me understand a little bit but is there anyone on here that has seriously disabling depression/homicidal/suicidal thoughts/etc?

It sucks because I KNOW from knowing her for the last 6 years how bright and wonderful and warm she is. I know the real girl beneath all the darkness she has to battle everyday.
On her good days she's incredible and a joy to be around.

When the bad days hit though it's so hard to know what to say or do.
I don't take anything she says personally. I always just give her the "It gets better" schpeel and when she has a good day I try to take advantage of it and talk about different things that help her when she's down.
She likes when I make list of things we want to do in the future like going to the zoo or helping me shop for apartment when she's freaking out. It also helps to remind her of her surroundings and who shes with and who she is.

I don't know.
It's getting a lot harder. Especially with her manic episodes. My sister has bipolar disorder so I grew up around that. The mania is like being around a little kid though, it can be fun but also annoying. I know she can't help it though.
And the depression is just awful. It's scary sometimes to hear her deepest thoughts.

Advice on how to support and handle situations?
Thanks

Am reminded of the end of "What Dreams May Come" how Williams' character stays with his delusional depressed wife knowing he'll become just like her. In the real world though, happy endings are few and far between. But if there's sign of hope and she does better with you around, go for it. But as with the advice in the movie, you have to accept the possibility she isn't going to get better, and staying a part of her life is just going to bring you down along with her.