Obstruction after sacrifice fly

[falsecut]

NFHS rule question.

Runner on third. Fly ball hit to left fielder who makes the catch. The runner properly tags and heads home down the third base line. The catcher is anticipating the throw and has moved to a position straddling the third base line, about three to four feet up the line. She is directly in the path of the runner at this point. The ball is thrown in from left field on the fly and takes the catcher inside the diamond after which she receives the throw and diving to the plate tags the runner just before she slides across it.

We would definitely have obstruction had there been a collision prior to the catcher having received the ball for instance. My request is for opinions on how far up the line it might seem the runner would have to be for obstruction not to apply in this case. There is nothing "complicated" as it were in this play, just a straight tag up and go home play with the catcher having been in the direct path home at some point.