One most important thing, is let her know you are there for her. You can even offer to drive with her to her pdoc appts., so in between her session, she'll have the comfort someone is there, cause it can be scarey sometimes.
You can be there for her in a sense, to encourage her to stick with treatment and pdoc appts.,contact doc if any unusual side effects of meds start to occur.
Sometimes it's also a good idea to elect yourself or suggest to her that you become a laison,in case she should ever feel, or you feel she is fallen very deep into a possible tragic depression, this applies to the opposite too, if she starts to show signs of manic episodic behaviour, sometimes it can just be mild mania but it's best to safeguard against an oncoming,full blown episode.
You'll need to sort of custom design what is comfortable for both,some books,literature and support group meetings for those who care for someone with a mental disorder(s) can be of help with suggestions. If she allows you, her pdoc may also be able to offer some suggestions.
I know it can be confusing and overwhelming, I've been on both ends, my oldest brother is BP-I and I've been a huge support to him and his wife. I was DXed with BP-II(mild) and ADD(mild) so I have a good understanding of how both ends can be.
I hope this was of some help.
Please take care now,
DE