It is definitely a struggle to live with. Her level of depression seems to go in cycles, sometimes lasting months at a time. If you don't have depression or live with someone who suffers from depression, it is difficult to understand the magnitude of the disease.
Goodness, dc, that sounds like bipolar disorder.
The "struggle to live with" stuff you describe is true. The best description of the "mixed state" I know of is "chainsaw personality" as in "the chainsaw school of human relations".
Recurrent depressions lasting weeks and months are typical with bipolar II. So is a real mean streak. Just to cap the whole thing off bipolar disorder gets worse with time.