A big problem with psychological disorders is that they can be sneaky and resemble each other - BIG time. There are certain spells I have where others would ask me to my face if I had ADHD, too, and I couldn't give them a straight answer ... until the next cycle hit and it went away.
Having that much mental history among her family can be a predisposition to alot, but her pdoc needs to make that final call. And if you doubt it, don't be afraid to ask for a second opinion - just make sure it's from a fresh doc, in a different clinic.
What I did was, to prevent any possibility of there being a 'leak' between one office and another causing an influence on the new doc's say, I just kind of ... well, I lied. I said I'd never been dx'd with anything, hadn't seen anyone, and started as if I truly hadn't. With that done, she of course didn't even ask to have my previous doc's contact information because to her knowledge, there wasn't one.
If your daughter IS bipolar, it's not the end of the world or even in some cases more difficult - just different. BP is variant for everyone who experiences it. Just take it one day at a time, breathe through it and help her track her moods and learn coping strategies.
For yourself - again, just take a deep breath. If she truly is, it doesn't mean you've lost her, or don't know her at all. It only means there's more to love about it her. It took years for my sister, who I'm very close to now, to admit I wasn't just full of myself once I was diagnosed. When she did start realizing maybe it was true, after she saw some very marked episodes, she began to have more patience and worked with me but still avoided the issue. Only last year, she finally worked up the nerve to ask me what it was like ... I told her "take the strongest emotion you ever remember feeling. Take it and close your eyes and try to remember exactly what it felt like ... now multiply that by ten. That's me, every day."
It stunned her, and she hasn't once tried to convince me the docs are wrong since. Oh, she still gets prickly and snaps back and gets upset when I'm in a vicious mood, but she's also quicker to let it blow over, and accept my apologies when I realize later how much of a jerk I was. =p
Adjusting and adaptation is a lot of it. You'll both have to adjust, not only to the idea but it's reprecussions. Because if she truly does have BP you both need to be aware it truly isn't going away, and unfortunately in a lot of cases it can get worse later in life, depending on the approach you take for it.
((hugs))
~ San
:: Living is more than just being alive - Anberlin ::