CalPolygardener said: It would drain better if it was filled with the same soil as what's around it. You have created a perched water table. Water won't go into the rock/gravel until the soil above is saturated and won't go into whatever is below until the rock/gravel is saturated. Talk about poor drainage!
If she is filling it with clean rock, not gravel, it will drain well.
I have put in dry wells, which are holes in the ground , x feet deep, filled class 2 or 5 crushed granite that drain quickly, often put where a down spout ends.
Assuming the hole she made drains (some clay soils, especially if it is fill for building DO NOT DRAIN well. We used to replace a lot of trees planted in clay fill that did not drain. So we had to post hole drill till it was pierced ) but if the hole she dug when filled with water drains at an accepted rate, the water will filter through the rocks to the base quickly.
IF it does not drain a wet garden will look nice.
