The Grigri's primary advantage lies in its ability to catch a falling climber more effectively than the ATC. It reduces the risk of belayer error, making it a reliable choice for climbers of varying experience levels.

With a GRIGRI, it is not possible to rappel on the two strands coming out of the anchor. So one must rappel on a single strand, blocked at the rappel ring by a knot attached to a locking carabiner. Rappel only on the strand opposite the knot block; the other strand is used only for retrieving the rope.

noun. gri·​gri. less common spelling of gris-gris. : a talisman, amulet, voodoo charm, spell, or incantation believed capable of warding off evil and bringing good luck to oneself or of bringing misfortune to another.

Daughter is using a Grigri as a self-belay device. This is expressly discouraged by Petzl, the manufacturer, on this page titled Self Belaying is Prohibited. That's pretty damning. As the page admits, some people do use a Grigri for self-belays, but it's not ideal and potentially dangerous.