Calling a runner out for running inside the base line

Question
My 16 year old daughter is umpiring for our local recreation department softball league.  At tonight's game, the catcher dropped the third strike and the batter ran towards first.  She ran inside the base line rather then in the lane on the foul side of the base line, interfering with the catcher's throw to first.  My daughter called the batter out.  The coaches and the parents did not like the call and even her dad said he wasn't sure about the call she made.  We've looked through our rule book, but have been unable to find anything beyond the interference call, which is a judgement call.  Can you tell me, did my daughter make the right call?

Answer
Hi Tamara,

If the throw is coming from foul territory and the defense is using the colored portion of the base, a b-r may run in fair territory w/out being called for interference. Since any throw coming from foul territory on a force at 1st the defense and the offense may use either bag it is a judgment call. All interference calls are judgment calls.

If the throw was coming from fair territory, they must run in the lane.

Mark