Honestly just read her the first two paragraphs of this post. That's way more than most people even try to do. You're going to be just fine! I think a lot of it is going to be specific to her, and where she is in treatment. Once she's settled into whatever routine works for her, it probably won't be too noticeable that she has anything. But it sounds like she is figuring out the right regimen, so it could still get dicey. The only time I was ever hospitalized was when I was finally getting treated -- a lot of the medications they give you can have some serious side effects, and you really don't know what will fuck you up until you try it. Getting on the right medication can be like playing a game of Russian roulette. Just keep that in mind.
Do you know if it's bipolar type I or type II? I have type II and hypomania is a nonissue. If she is describing her manic episodes as "hyper" I am guessing she is similar. I personally talk a little faster, sleep a little less, and start a bunch of projects I'm not going to finish. I wrote 3/4 of a novel in about a week, once. The only person who usually notices I am manic is my therapist.
Depression is harder. It's frustrating because it doesn't feel like there is any reason for it, but you are just less able to function. Socializing takes a huge amount of effort and is painful. It tends to be easier to shut people out then have to deal with them. It takes practice to get better at not doing this. Depending on where she is in treatment you guys may need to work on it. I think this is one of the harder things for loved ones to deal with.
It also gets harder to do other things. Stupid, mundane things like brushing your teeth or cleaning your room or responding to emails. I am not really sure what the best way to deal with it is. It usually helped when my ex would say "let's put on a movie." It was distracting and easy to watch stuff on Netflix. Try to avoid saying things like "it will get better." Mental illness definitely skews your perception of time. When I am depressed I feel like I have always been depressed and genuinely feel like I will always be depressed. There's a certain kind of hopelessness to it. Even if I know for a fact I will feel better in a few months or a few weeks from now, that information is meaningless because I can't remember what happiness feels like. Also avoid saying "X thing is easy, just do it!" That's a sure fire way to make someone who is struggling with something feel incredibly stupid for struggling with it. Also try to avoid pathologizing her emotions. It's draining to have a partner ask, "Is this an upswing? Is this a downswing?" every time you have a feeling. And even if it is mania, or depression, calling it that as an outsider can sometimes make feel like you are minimizing it, making those emotions less valid than other ones, when they are absolutely 100% real.
But good communication with her is going to be the key. And hopefully she is a good communicator as well, even if she is a bit guarded right now.