Obstruction or an out?

[Rachel]

NCAA 1st play of the game(of course). The batter slaps the ball past the 1st baseman who charged on the play. The 2nd baseman fields the ball and is debating on taking it by herself or tossing ot the 1st baseman who is running along side of the runner (who was legally running in the lane). At the last second the 2nd baseman takes it herself. The out is made on the force just as the runner and the 1st baseman tangle up and fall down about 1ft. away from the base. There is no saftey base so the runner has to come over to the bag. At what point is this obstruction? I know this is a HTBT but give your thoughts.