Its extremely admirable that you want to give her such support. She is very lucky to have someone like you in her life. However, you can't keep banging your head against a brick wall like this. When I was single, I didn't see a problem with my BPII. It enabled me to work harder, be more successful and take 'risks.' I travelled the world, met some great people. When I got married, expectations changed and I pushed against it. I found it hard to control my moods within the natural boundaries of marriage. It was a struggle - often him telling me to seek help, but as far as I was concerned, there was nothing wrong with me and I resented him for suggesting there was. At the same time, I was plagued with guilt for my treatment of him and I hated myself for not having any control. When we later had children, I found it even harder to cope. Sure, those nights when I couldn't sleep were great! I could take care of a sick child, clean the house, go for a run and not look look tired! There were 'dark' days too, but no one outside of the house would know. Just my husband, who would struggle to coax me out of bed. My children as they grew older would ask why Mummy was in bed all day, they got used to Mummy being 'sick' And then Mummy being angry and Mummy going out all night. The responsibilities I wasn't taking seriously started to creep up on me. After one particularly bad low, I sought help, not for myself, but for my family. The diagnosis was made and a treatment plan has been put in place. For the first time in months, I have really been 'myself' more relaxed, more focused and my relationship has improved greatly. Learning about the illness resulted in initial denial, but its been a relief to know that I'm not nuts! Its a comfort to know I'm not alone in my moods. I did take medications, but with professional consent, decided I didn't want them, now I manage myself. However, I have BPII, in your girlfriends case, she clearly has BP, which can be hereditary. Like a diabetic, she needs treatment, or else she stands a very real chance of hurting herself or/and ruining any chance she has at a normal life. I don't know her, so I can imagine how best to broach the subject, but I think its best if you research as much as you can. Learn how best to respond to her and if necessary speak to a Dr to get advice. Then carefully broach the subject (when she's in a completely normal mood), explain what you've read and reassure her that you'll love her regardless. If she knows she has your unconditional support, she can take some time to mull over the information. Get her some books to read, perhaps, 'An Anquiet Mind - Dr Kay Jamison.' And some other autobiography 'A Brilliant Madness' have a look at amazon.com for some ideas. You need to take control of this initially, because she won't be able to. She'll have questions, which you can encourage her to find answers through a medical professional. Go to her appointments (if she wants!) and help her through this. Its quite a journey. I'm sure that in the long run, she'll appreciate having a diagnosis and knowing that she can manage this quite easily. I'm sure she's terrified of losing you, and if this carries on, she will lose you. But be strong and get her the help she needs.
All the best