I always provide a container in the cage of egglaying females so they can dig to show you that they are ready to lay eggs.

Veileds can lay eggs without being mated...but some do and some don't. Part of it depends on their diet and the temperature they are kept at. Overfeeding them can make them produce large clutches and that is thought to shorten their lives.

Eggbinding can indeed be caused by not providing a proper place for her to lay her eggs....but husbandry issues and physical problems (fused eggs, deformities in the reproductive tract, etc.) can lead to it too.