(From wikipedia) 6 degrees of separation, also referred to as the "Human Web", refers to the idea that everyone is at most six steps away from any other person on Earth, so that a chain of, "a friend of a friend" statements can be made to connect any two people in six steps or fewer.
And there on Chloë's twitter she says:
..first scene me and Sir Christopher Lee ...
And my point? Well the father of a friend of mine knows Christopher Lee. So the theory seems to work!