What's the proper coverage on this play?

[azbigdawg]

Had a similar play last night in a fed game..Line shot to f4 who fired to first to get the runner off of the base... runner dives back in... I cant tell if the tag is made... (Im In "C" position) so I call "safe". The first baseman looks at me as if Im smoking crack on the field. The coach calls time and asks me If I would ask my partner for help. I tell him yes (why WOULDNT I). I go to my partner, and he tells me that the runner was definitely tagged before she got to the bag. I tell the other coach that the runner diving back to first was out.... and she doesnt say a word.. The bottom line is to get the play right. Period