I hate my magpies and would never dream of feeding them on purpose but if putting out 6 chicken eggs kept them away from the duck, that's a no brainer. Do you have some scraps of wire around?
Crows, jays and magpies are all egg thieves. They are relentless. I would either move her which could make her abandon the eggs or take a wire dog crate and place it over her where she is.