need a little help I have confused myself

[tidefanintenn]

Here is the situation: r1 on first batter hits pop up in vicinity of bag. Runner is standing on bag and never moves. Fielder coming over to make play runs into runner and both fall to ground. The ball lands about a foot in front of bag and rolls into foul territory without being touched. What would we have. This was in a high school game. I called foul ball and left it at that, after the game the defensive coach said he would have liked to have had the interference. Help me figure this out PLease. I feel like the runner was doing what she was supposed to do and did nothing to create any interference but I also think the fielder has the right of way to make the play. Thanks guys for the information in advance.