Positioning related to other players

[Scrapper1]

In judging whether one player is behind another player for the purposes of identifying overlaps, does the back-row player have to be closer to the endline than the front-row player? Or does it only matter that the front-row player is closer to the center line?

In other words, suppose the setter is pushed up to the net and the front-row player has a foot clearly closer to the net than the setter, but ALSO has her other foot closer to the endline than the setter. She's essentially straddling the setter's position.

Not that I would ever call this, but is this technically an overlap? Or does it ONLY matter that the front-row player's foot is closer to the net than the setter?