There are some great responses here. Please take them for what they are worth; respectively. Everyone here means well, and with much care and concern.
During a manic episode a person is so unglued from reality that they cannot comprehend the difference of what is right from what is wrong; they simply have their head stuck in the sand. If a person is hallucinating and is in psychosis believing that their 'marriage is over' or is 'having problems' when in reality it 'is not', then that person will believe the psychosis hallucination- not the reality of the truth. Only because they are a) not taking their meds or b) simply severely manic and need their meds adjusted or c) both a and b.
Things do happen like that. A person will hallucinate stupid crap like that, or believe in things that are 'false beliefs' and think that their family is out to get them, and then run from their own family for fear that their family are people whom they should not trust. That is a person who is in a 'manic phase'- and it is COMPLETELY chemically caused; not controlled by their own selves. They are very sick, need help, and need to be placed in a hospital; immediately.
Whether or not a family member or friend is able to place that person in a hospital, is another story. That is a different scenario. And, to prove the fact that the person is that manic is another story as well. Sometimes in certain situations a person must be very suicidal to be admitted into the hospital verses being just manic; and that really stinks. That is the case in my state- and it royally is the pits.
If you do love a person who is like this, then do something about it. You are a part of the relationship too.
I wish I had oodles of advice to share but I don't. Living with a Bipolar Person is like riding the waves in the ocean. It can sometimes be rough out there, and sometimes be very calm. You just never know how the tides will be or when the hurricane will hit.
Hang in there and keep us all posted.