Runner interference with no slide

[rafking]

Situation:
12U girls playing NFHS rules at first game of season and medium to low skill level. BR hits grounder to F6. The throw is over thrown to 1B. Runner on the way to second. Here comes the throw from F3 to 2B to try and get the runner. The throw beats the runner (barely) and fielder bobbles the catch as the runner does not slide and the girls meet each other standing up.
As PU I clearly see that the actions of the runner impacted the fielder's ability to catch the ball, but no call from BU. I did not have a clear view if runner touched fielder as trying to catch the ball.

a) If no contact between fielder and runner, then I agree nothing to call.
b) If runner makes any sort of contact with hands or upper body (even an ever so slightly bump) as the throw is trying to be caught, then I can see interference.
c) If there is no chance to get the runner out, does this matter in making the call

Am I thinking of this in the right way?