I would think that the shortstop should be covering second base. If there are runners on 1st and 2nd, they should cover the base to present the option for a force out. If there is just a runner on 2nd, they should cover in case the runner goes back when the 2nd basemen throws to third, in case of a run down.

Yes I agree shortstop should cover 2nd base. If play is at 3rd the left fielder should be backing them up.

The short stop should cover 2nd base for a double play or if the second baseman sees that the closest play is at 2nd

LEFT FIELDER!!

shortstop goes to 2nd base and left field covers 3rd base

http://www.softballperformance.com/softball-fielding/developing-an-outfielder.html