You should be expecting the double play... therefore you should be moving towards 1st. F4 should be expected to either come up firing to 2nd or attempting a tag. When she attempted the tag and then turned to 2nd this says she missed the tag. No call is in order until the force out is made at 2nd.
Can you guess an out? No. Guess a safe. No. If you don't see the out then the runner is safe and this would not be considered a guess. If you missed seeing an out then you are out of position... this happens. Learn from it and get into proper position next time.
Because you are expecting the double play, you have got to give up 3rd base to the Plate umpire who should be moving up the 3rd baseline to either make the call at 3rd or to move back towards home as the player advances past 3rd.
I would have expected your position to come from behind F6 towards the pitcher's mound or slightly towards 2nd. F6 will be heading to 2nd and you should come into the diamond behind her. When you make the call at 2nd you should be nearly inside the diamond - close to the 2nd-3rd baseline. Progess towards 1st and make the call at 1st from near the pitcher's mound.
At least this is the way I would envision the play to unfold.
