Here "she" refers to Ariel, which represents the people of Ariel. Alternate translation: "the people of Ariel will" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The words "mourning" and "lamenting" mean basically the same thing and emphasize the intensity of mourning. Alternate translation: "they will mourn deeply" (See: [[rc://en/ta/man/translate/figs-doublet]])