Is the work of a fiancée who works as a secretary in a foreign company and interacts with men considered impermissible (haram) or permissible (halal) after marriage, especially since her fiancé is unemployed and she fears financial hardship after marriage?

A woman's work in a place where she mixes with men is forbidden unless she is compelled to work, such that she has no one to support her, and she cannot find a place free from mixing, and the rest of the conditions and legitimate controls are met. The questioner is not compelled to work in this mixed environment, whether before or after marriage.