Obstruction

[teebob21]

Was the ball in the possession of F5 at 3B at the time of contact? If so, R2 is already retired. A retired runner cannot be obstructed.

Did R2 impede or hinder F6's attempt at making the play/throw? If so, R2 is out for INT.

Was R2 clearly beaten to the base by the ball? If so, R2 is out, as a runner clearly beaten by the ball is not protected if they will clearly be out with or without OBS (NCAA 9.5.7.8).

If none of the above apply, call OBS. R2 will be awarded 3B, as she is forced to 3B by the BR and R1.

Or call nothing:
12.13.3 Simply because there is contact between the defensive and offensive
player does not mean that obstruction or interference has occurred.
Note: The first fielder fielding a batted ball is protected from obstruction, but
thereafter, if both the fielder and the runner are acting appropriately, neither player
shall be penalized for the incidental contact.

The "clearly beaten" exception is probably what the partner was referring to, when saying if the runner is dead-to-rights out, we don't call OBS in NCAA.