What is your advice to a wife who doubts her husband's love for her, claiming that he desires polygyny, even though he has never brought up this issue with her, especially since polygyny is forbidden in Tunisia?

Polygyny is not necessarily an indicator of a lack of love or loyalty to the first wife. The Prophet, peace and blessings be upon him, married other women in addition to his existing wives, and he is our role model in loyalty and kindness, as he said: "The best of you is the best to his family; and I am the best of you to my family." He married other women in addition to Aisha, may Allah be pleased with her, who was the most beloved of people to him, without that affecting her status or his love for her.