The first thing to understand is that wiring something to a ground rod is not the key part of safety. The key part is wiring all metal objects together.
The first (1) point that matters is that all metal chassis must have wires connecting them together (including between multiple trailers, storage containers etc.) "bonding"
The second (2) is that no currents from any circuits is allowed to flow through those bonding wires. All circuits have their own power wires and return (or "neutral") wires, forming a loop from source (battery or inverter) through loads and back to source. The circuits do not use "ground" or "bonding" wires to carry current.
The third (3) is to have one or more ground rods and connect the bonding wires from (1) to that ground rod. Also connect any pipes like water, gas, etc. All exposed metal is pulled to same voltage as the earth with ground rod.
A fourth (4) is to use GFCI outlets for any wet locations including outside. (not the issue in this case)
The shock may have occurred because a life wire had a path to the container your daughter touched. Alternatively, the container may have had a path to chassis of equipment, but a live wire had a path to earth, so earth and container were different voltages.
One of your photos shows PV panels on the roof of a container or trailer. This situation has caused shocks for a number of people because inverters like yours superimpose AC voltage on PV+/-. There is capacitance between PV cells and PV frames, causing high voltage but low current. For that reason, The First (1) rule to bond metal together, PV panel frames to container back to inverter chassis to building inverter is in and to a ground rod.
Then test everything on AC and DC scale, voltage to chassis and voltage to earth.
