Is it permissible for a nephew's wife not to greet her husband's paternal uncles with "Salam" or to sit with them in the presence of their wives, knowing that she goes out to visit her own family?

Marriage establishes a marital relationship between the husband's family and his wife's family. This relationship is not like the ties of kinship that are obligatory to maintain. The ruling on a wife meeting non-mahram (definition) relatives (such as the husband's brothers and paternal uncles) differs from the ruling on meeting mahram relatives (such as the husband's father and grandfather). Islamic law has warned against non-mahrams entering upon the wife, such as the in-law (Hamu) whom the Prophet likened to death. Therefore, privacy with them is not permissible, nor is shaking hands with them, nor uncovering what must be covered in front of them, and none of them should enter upon the woman alone. As for exchanging greetings with them and returning them in a manner free from suspicion, this is permissible, and a woman's voice is not considered 'awrah according to the most correct opinion. If a woman feels shy about meeting them, she is not to be blamed for that, as she is not abandoning an obligation, and she should obey her husband if he commands her to abandon what is not obligatory.