"My girl-friend thinks that her life is in danger of a Titanic type of event on the Alaska voyage. Is there in any merit in her fears??? What safe guards do modern ships have to prevent late night disasters???"
1. Modern cruise ships have incredible equipment, including access to satellite tracking of iceburgs of any size. Knowing exactly where icebergs might be, it's very easy to avoid the area.
2. Modern cruise ships are divided into many watertight compartments below the water line. The number of compartments that you would have to flood in order to endanger such a ship is so great that no single iceberg could possibly do it.
3. Modern cruise ships also have adequate lifeboats and liferafts to accommodate all of the passengers, officers, staff, and crew in the event that something really unthinkable does happen.
"Finally, how close do the cruise ships come to the Icebergs??"
As others have said, no captain of any cruise ship is going to put the ship in any danger whatsoever. You can be sure that the ship will remain a safe distance from any large chunk of ice that breaks off of any glacier.