Her tears at last revealed her vulnerability. Lureen was described a cold, cool, shrewd business woman, who does not even care much about her own son. But I believe she loved Jack, yet she was never loved back the same way. As such, her hair became more and more blonde, and she buried herself and her affection to Jack much deeper inside. At last, as she finally heard the voice of whom Jack has loved for life, all the love, the disguise, the sadness overwhelmed her, so the tears... I think that was a very subtle moment, and Anne Harthaway(?) has acted it nicely.

I agree, to be tough and cold is her character. That is why her tears tell so much....