Does saying "for God's sake" or "by God's life" constitute disbelief, and does hearing talk about horoscopes make a person a disbeliever?

There is no harm in saying "min shan Allah" (for God's sake), nor is there any harm in saying "wa hayat Allah" (by the life of God), as it is an oath or an appeal by one of His attributes. And hearing what the girl said does not make you an unbeliever (kafir). Remaining silent about a Munkar (evil/wrongdoing) is a sin, not disbelief (kufr), and you did indeed object to her.