When we deliberately turn our backs on God and shut Him out of our lives, we always pay a price -- always. It may not be obvious at first; in fact, the Bible acknowledges that sin's pleasures are often "fleeting" (Hebrews 11:25). But eventually our determination to leave God out of our lives will catch up with us.
Often it catches up with us in this life. Yes, your friend may seem happy and free from troubles, but is she really? What about the moments of loneliness, or emptiness, or boredom, or guilt? And what will happen when she faces a personal crisis? Where will she turn then for peace and strength? The Bible's words are true: "There is no peace ... for the wicked" (Isaiah 48:22).
But living without God also catches up with us in eternity. Someday we all will pass from this life into eternity, and there we will meet God. Why should we expect Him to welcome us and give us eternal life if we haven't wanted anything to do with Him in this life? Some of the most sobering words in all of the Bible are these: "I never knew you. Away from me, you evildoers!" (Matthew 7:23).
Pray for your friend, that she will see the foolishness of her ways and turn to Christ for the forgiveness and new life she needs. Pray, too, for yourself, that you will be an example to her of Christ's love and peace.