Are the nights the second wife traveled with her husband for work counted as part of her right to Mabit (overnight stay), or are they divided between her and the first wife?

If a husband travels with one of his wives for a benefit that cannot be achieved otherwise, he is not obligated to compensate the other wives according to the Maliki school. The Hanafis hold that the Prophet's practice of drawing lots among his wives before traveling is to be understood as recommended, not obligatory, and a husband may travel with whomever he wishes without having to compensate those with whom he did not travel. The Shafi'is permit choosing the wife who is suitable for travel, except in the case of travel for Hajj, military expeditions (ghazw), or visiting the Prophet (peace be upon him), in which cases lots must be drawn among them.