Is the money taken from a man who claimed to be a prince and gave it as a gift with the intention of marriage, then a lawsuit was filed against him and she won the case, considered permissible (halal) or forbidden (haram) when given to the father for investment without interest to pay off the father's debt?

This money was either paid for the questioner to obtain something unlawful from it, in which case it is impermissible for him to benefit from it or to return it to the payer. Rather, it must be given in charity and spent on the welfare of Muslims. Or it was paid with the aim of completing the marriage, and since the marriage did not take place, this money must be returned because it takes the ruling of a gift for recompense (hibat al-thawab). And he who gives a gift for recompense has more right to his gift as long as he has not been recompensed for it. The questioner is advised to repent from sinful relationships and to close the door to them by refraining from conversing with non-mahram men.