Is it a sin for a married woman to abandon adornment (henna and kohl) out of consideration for her paternal aunt's feelings, whose husband has passed away, and is it obligatory to seek her husband's permission for that?

A woman is not permitted to mourn for a deceased person for more than three nights, except for her husband, for whom she mourns for four months and ten days. This is based on the hadith narrated by Umm Habiba (may Allah be pleased with her): "It is not permissible for a woman who believes in Allah and the Last Day to mourn for a deceased person for more than three days, except for her husband, for whom she mourns for four months and ten days." It is not permissible for her to mourn beyond that for the sake of anyone's feelings. What is obligatory is to seek Allah's pleasure, and whoever seeks Allah's pleasure, even if it displeases people, Allah will suffice him against the burden of people.