All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It is prohibited for the wife to ask for divorce without a lawful reason such as the husband’s injustice towards her or his debauchery or immorality. Thawbaan reported that the Prophet, sallallaahu ‘alayhi wa sallam, said, "Any woman who asked for divorce without a lawful reason, the scent of Paradise will be prohibited for her." [Ahmad]
Consequently, if the wife has asked for divorce without a lawful reason and her father helped her, then both of them are sinful.
As for returning to the husband’s house after divorce, if divorce was revocable, then she should not have left his house, and her husband has no right to force her to leave until her ‘Iddah (waiting period) lapses, as Allaah The Almighty said (what means): {O Prophet, when you [Muslims] divorce women, divorce them for [the commencement of] their waiting period and keep count of the waiting period, and fear Allaah , your Lord. Do not turn them out of their [husbands'] houses, nor should they [themselves] leave [during that period] unless they are committing a clear immorality…}[Quran 65:1]
If divorce was irrevocable, then she is entitled to alimony and housing as long as she is pregnant, until she gives birth to her child (See Fatwa 83934).
On the other hand, the fact that this pregnancy took place against the husband’s wish does not affect the wife’s right to housing, noting that the husband has no right to prevent his wife from getting pregnant if she wishes to have children. Nevertheless, the wife is sinful because she lied to her husband. For more benefit, refer to Fatwa 84086.
However, the wife made a mistake by breaking into the house of the husband, and she should have demanded that he provides her with a proper accommodation. If he refused, then she has the right to take her case before a judge to force him to provide her with a proper accommodation.
Finally, there is no doubt that the father of this woman is wrong in threatening to kill this man.