What is the reward for a wife when her husband desires intimacy and she is unable, yet she does not let him feel that out of fear of displeasing Allah?

A wife's good devotion to her husband carries a great reward. If a woman obeys her husband, guards her chastity, and performs her prayers, she will enter Paradise. Her patience and endurance of hardship in obeying her husband, seeking Allah's pleasure, increases her reward and status, and demonstrates her sincerity and devotion, for the reward is commensurate with sincerity, not with hardship.