complicated mess - Is my wife Bipolar?

Hi - 6 month ago my wife lost her brother to suicide. Since then she has undergone a total personality change. Prior to this event she was the most caring and loving wonderful wife who would never hurt me or my two grown up sons. It started when she stayed out all night with a man she now says she loves. She has left me at least 8 times now, because of her feelings for him, four of which she ran to him. When she goes to him she is in a manic or elevated state and takes no account of consequences or her safety. She barely knows this man, who has some serious mental baggage of his own, but is obsessed with him. She appears to cycle from depressed to manic on a 2 week cycle. She has increased energy levels and requires little sleep during the manic episodes. The manic episodes seem to build up slowly over a period of days, maybe 5/6, before she flips and runs to this guy. Unfortunately the very next morning she comes crashing down and feels terrible / extremely guilty about what she has done and then runs immediately back to me, which is destroying me. She then has a period of low mood, about 4/5 days before the gradual build up to manic state. She swings from telling me she loves me and is sorry to telling me she dosnt love me and wants to be with this guy. She was taking the anti depressant Sertraline which, the psychiatrist said was pushing her into a hyper state and that she was probably on the edge of the bipolar spectrum??? She was admitted to a Psychiatric unit after threatening suicide, following an overnight stay and her first sexual encounter with the man. She was diagnosed with "Complex Reactive Grief". This diagnosis was based on information from a Councilor my wife was seeing through work. They think that it is complex reactive bereavement in which she is trying to replace her brother, who died 7 month ago. She has hardly grieved for her brother at all. She is now staying with friends who one of which is diagnosed with bipolar. She is now telling me that she is bipolar because she has all the symtoms. The psychiatrist has prescribed her Quetiapine.

MY QUESTION IS
- DO YOU THINK THIS IS BIPOLAR OR SEVERAL MENTAL ISSUES CONFUSING THE DIAGNOSIS
- AND - IS SUCH RAPID (2 WEEKLY) CYCLES A SYMPTOM OF BIPOLAR?

Please, someone help me - Im going downhill!