The ruling on shaking hands with one's brother's maternal sister

Question:
I have a brother from my father, and he has a sister from his mother. My uncle has married her. Is it permissible for me to shake her hand?

Answer:
No, she is a non-mahram to you. Your brother's maternal sister is not your sister; she is a non-mahram. Your uncle's wife is a non-mahram. However, you should greet her while maintaining hijab. As for shaking hands, no, hijab is required, and shaking hands is not allowed. You should only greet her with words, such as, "How are you, so-and-so? How are your children? How is your father?" There is nothing wrong with that.
As for shaking hands, no, except with a mahram, such as your sister, your paternal aunt, your maternal aunt, your mother, your father's wife, your grandfather's wife, or your son's wife; there is nothing wrong with that. As for your uncle's wife and your maternal uncle's wife, no, they are non-mahrams.