To properly manage her soil and prevent situations similar to the Dust Bowl, the best approach would be to allow plants such as grass to root in it.
Healthy root systems of plants help to anchor the soil, prevent erosion, and improve soil structure. Grass and other ground cover plants can also contribute organic matter when they decompose, enhancing soil fertility. Additionally, maintaining vegetation cover helps to protect the soil from wind and water erosion.
The other options, such as frequently digging the soil or removing humus, can lead to soil degradation and increased erosion, while simply watering frequently without proper vegetation management may not be effective in the long run.