Is it permissible for a woman to refrain from greeting and shaking hands with, and wearing the hijab in front of, her daughter's husband?

All praise is due to Allah.

The husband of a woman's granddaughter is one of her mahram relatives through marriage. It is permissible for him to see of her what he sees of his mother, sister, daughter, and other mahram relatives. Her covering her face, hair, or arms from him is an excessive strictness in hijab, and her refraining from shaking his hand is an excessive caution. This may cause aversion and estrangement. Therefore, she should abandon such strictness unless she senses suspicion from him or finds a treacherous gaze from him.