Is it permissible for the son's wife to greet the mother's uncle, who visits them once a year and is around 70 years old, knowing that there is no kinship between them?

The maternal uncle is a stranger to his brother's son's wife, and his ruling concerning her is the same as that for other strange men. Therefore, it is not permissible for her to shake his hand or to appear before him except with her legal hijab, even if he is an old man, because the Prophet, peace and blessings be be upon him, said: "For one of you to be stabbed with an iron needle is better for him than to touch a woman who is not lawful for him." And touching is more severe than looking, so anyone whom it is forbidden to look at, it is also forbidden to touch.