The reported police complaint by her was out of fit of anger without considering the consequences involved in it.
At Least her parents should have convinced her but they supported her taking her to police station instead.
Actually her parents are to be blamed for her unruly and provocative behavior because it must be due to their instigation that she went upto police station.
Now she has realised her mistake and regretting for it and also pleading to take her back. To err and forgive is human.
Your brother should be adamant now.
He should think of the opportunity being given to save his marriage.
In my opinion your brother and your family members should apologise her now and take her back with an assurance from her (orally) to not to indulge in sch activities in future and save sacred institution of marriage atleast for the sake of the infant and innocent child..