It can be scary to get diagnosed with a long term disorder. But the truth is that you need to be happy too if this situation continues you probably won't be happy. You probably have better luck in trying to get her to do something about her problems when she is a contrite mood rather than an irritable one. Also, have you considered that she might have borderline personality disorder. With that, one of the symptoms is that a friend/love one is wonderful or the worst possible person. Seeing things in black and white. You could look at webMD.com or wiki.com for bipolar and borderline personality disorder. There is therapy, I think DBT, for BPD. Sometimes they medicate BPD with similar medicines used with bipolar.