Infield fly rule

[boldfacesun]

I would like clarification on a rule that I also thought I understood from a coaches perspective.

Bases were loaded, 1 out. Hitter pops up just over second base, umpire yells "infield fly". The runner on 3rd base had taken off with the hit and she was trotting back to 3rd to tag back up. The SS, who caught the ball, then threw to 3rd before the hitter got back and the umpire called the runner out. I always thought that until the runner tagged back up, they couldn't be called out. Please clarify.