Yes. If they're laying soft shell eggs, they're not getting the right amount of calcium to make the shell so, if she can eat as much as she wants/needs, that should fix your problem.The food she has contains oyster shell but you still think I should give her extra? Do you mean hand feed it to her daily or provide it in a dish?
I would personally give her another dish.
Then it's optional to her, and not 'forced'.