Three of the main “hidden” reasons, looking through the lens of Compatikey is their “Inner Style” is smooth and easy and their “movement chemistry” is easy/friendly. They also have a magnetic connection in their “chemistry”.
These two have the opposite Relationship and Plan Style, but with the other key things in a place of smooth and easy, this makes the differences less important, and probably helpful for this friendship.
Courtney has the Football Relationship Style with a Pencil Plan Style. Jennifer has the Basketball Relationship Style with a Pen Plan Style.