OP's case is complicated with the defense changing course and R2 advancing an additional base. It seems R2 reached 2B via FC since she was stopped and advanced when the defense made the throw home. It sounds like R1 didn't break for home until F2 made the throw. Here are some applicable NCAA rules.
14.15 Stolen Base Not Credited
14.15.1 A stolen base is not credited to a base runner who advances to a base with the aid of a safe hit, putout, error, force, fielder?s choice, illegal pitch, wild pitch, base on balls, hit batter, passed ball, interference, obstruction, or defensive indifference.
14.15.2 A stolen base is not credited to a base runner as a result of defensive indifference...
14.15.3 A stolen base is not credited to any base runner when any other base runner is thrown out on an attempted double or triple steal.
Exceptions:
1. On a double-steal attempt, with base runners on first and third bases, credit the base runner from first base with a stolen base if she advances on an unsuccessful but legitimate attempt made to put her out at second base, and the base runner at third base is thrown out at home plate on a continuous play.
2. With base runners on first and third bases, credit a stolen base to the base runner advancing to second base even if the initial throw is not to second base. The base runner must show the intent to steal.
3. With base runners on first and third bases, credit a stolen base to the base runner advancing to home plate even if the initial throw is not to third base. The base runner must show the intent to steal.