Is it permissible for a wealthy wife to donate the expenses of 'Umrah to her husband, and will she be rewarded for this act?

There is no objection to a wife donating to her husband the expenses for 'Umrah (definition) or Hajj, and she will be rewarded for it even if the husband is not poor, because voluntary charity is permissible for the wealthy, and it is considered a gift. The Prophet, peace and blessings be upon him, endorsed the charity of Zainab, the wife of Ibn Mas'ud, to her poor husband and her orphaned nephews, clarifying that she would receive the reward for charity and the reward for maintaining kinship ties.