Do you understand that a vector is a quasi mathematical concept in that it is really not defined as most mathematical concepts. A vector is an object that has length and direction. Given points the vector represents the direction "moving from A to B" as well as the distance from A to B, .
Where as represents the direction "moving from B to A" and . They have the same length but opposite direction.
So it has nothing to do with the point's relative to the origin.
If then and .