I'm not entirely sure of the question, but are you sure she isn't just going through molt, and has become irritated on the exposed skin, that would normally be covered by feathering? i have 3 LS and they do seem to become irritated when they moult,
if you think it is the ducks that are pulling her feathers then i would consider moving her, and upping her feed per day, killing wouldn't be my first thoughts, unless she is looking in pain i would leave her.
Good Luck