contact at the plate - must slide?

[fastpitch]

Let's say the catcher has the ball and is up the line and when she reaches to tag the runner there is contact and the ball falls out. I rule incidental contact and call the runner safe. The only contact was between runner's shoulder where the catcher reached out to tag her. If the runner runs into the catcher I call interference, but if a tag is being made and the only contact results from the tag I do not see obstruction or interference, just a dropped ball.