I doubt she'd be quite as passive and deferential in an American film.
Speaking as an American, I found the character adequate, but she didn't really sit well with me. I'd like to see a more equal power relationship depicted in such a modern intellectual household.
I assume you are speaking of the son's wife. Her character may not have been realistic, but realistic characters are boring. She was...wait for it...written to move the story forward, with her reactions, actions, and opinions.
The real value of the wife of the son was her moment where she said she thought her husband would never cheat on her, because he was too afraid of getting caught and losing her. She admired the father because he was trying to seek happiness. This totally shocked me (and her husband, which was the point). The son truly loved his wife, would never disrespect her, was disappointed in his father for disrespecting his mother, and here the most important person in the son's life did not understand that the son didn't cheat on her because of his sincere 'goodness'. She didn't value it, and didn't understand people doing anything other than for their own self interest.
If you are speaking of the father's wife, she is key to the story. The reason the son his a sincere and pure goodness is because of his mother. She lives by example. She gives unconditionally, never keeping score and absorbing insults, disrespect, etc. That is truly living the Torah (or Bible, or Koran, or any philosophy of life). So the ending of the movie was so perfect, the mother had read both her husband's and father's work (out of her own generosity and support, there is nothing in it for her to do so) and recognized the passage and understood what her son had done. And her slight reaction in acknowledgement of the moment to her son was HUGE! She understood what happened, and took a small bit of joy in seeing her husband faced with a truth that shocked him and his ego; the son had given him the prize unconditionally, until the son saw the father cheating on his mother and learning that his wife didn't value the 'unconditional goodness' of others. The mother felt the same way, and that is why she acknowledged (and approved) of her son's inclusion of the passage in the "statement of the selection panel."