Hi Savage,
I'm not the partner of a bipolar, but I have bipolar and I am married. I was only recently diagnosed and just started medication last night for the first time, but I have been with my now-husband for almost 5 years. I have been diagnosed as bipolar II, as opposed to Bipolar I, so my highs aren't as high and my lows aren't quite as low as some, although I get pretty down and irritable, yet I have no dellusions or anything like that. However, I did have a pretty severe problem with alcohol, and my husband doesn't drink. Needlesstosay, he's been through quite a ride with me and decided to stick it out. I'm a graduate student about to earn my masters, therefore, I've had quite a bit of success recently. But then the depression hit and I finally sought help.
I think the best advice I can give to you is to encourage her to get help and treatment. After being misdiagnosed with just depression all of my life, I have to say that I am pretty optimistic about this new diagnosis, and the posts on here about how treatment has helped so many obtain some semblance of normalcy in their lives and relationships might help her to seek treatment. I had a pretty terrible childhood and life, partially because of the bipolar and my own behavior, and some not. So, counseling is required for my treatment to be successful, not just meds. Maybe you can encourage her to read more about the successes of treatment and counseling so that she can see that it won't be a waste of time, that she can get help and get better. It takes time to find the right meds, so the sooner she finds help, the sooner she will start to get better.
I am currently in the throes of depression, and my husband and I, although the very best of friends, will still have our arguments and aggravations with each other like everyone else. I think it is important to remember that too when you're in a relationship, that not everything you're going to fight about has to do with the disorder. I worry about that quite a bit, as do a lot of bipolars I think. Even though we have an illness that affects our moods, we still have valid reasons to be upset with our partners. With that being said, I have also read the horror stories that partners go through with their bipolar spouses or significant others.
I think the first step is for her to seek help and treatment, and if you've already made a commitment to stick it out with her, try to learn to recognize a valid argument from one that has to do with the disorder. Also, you can find lots of support on here like you're doing, and can do a lot more research on the disorder to learn what life is truly like for her inside her head. I think it might help you to recognize when something is going on and how to deal with it appropriately. And finally, they say this is a life-long disorder that only gets worse with time. It's important for her to get help.
We're still learning how to do that, too (but my problems are more with work than my relationship). It's still tough though. Hang in there, and good luck.