Ladd's late winner earned Jo Potter's side a fourth consecutive victory in the league, as they now sit just three points off of a play-off spot.
In a game where defences were on top, it took a moment of pure quality from Palace's new midfielder to break the deadlock.
With Kirsty Howat fouled on the edge of the box, Ladd stepped up and curled her free-kick into the top corner on 86 minutes.
Palace stood firm and held on to claim all three points in South Yorkshire.
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