My opinion is that if the bad times are bad enough that she has difficulty functioning she should seek help asap regardless of how she feels right now. Otherwise I would just support her in coping as best she can. As to whether it is bp, I would think so only if the "fine" periods are actually much worse than she thinks from your perspective, i.e. she feels great but you can perceive her behaviour to be self-destructive. Are the "bad" periods depressive or mixed? Just my 2 cents but it sounds like depression without more info.