Actually square on the line. The lady wasn't even looking down. She swung through the ball and missed. I noticed that when there was another close line call later in the match, I heard the lady with the knee pads say " I can't do what they did" and called the ball IN. Good on her.
at 3.5, the two ladies should work on the form and technique of the backhand volley. Also if you want to play longer without injury, got to learn to backhand volley with back of the hand facing out. Your elbow will thank you and won't develop tendonitis.