I think the answer is:
Artemis fowl (In the seventh book, "The Atlantis Complex")
A maiden huntress, whose life was brief
in the ancient Greek religion and myth, Artemis is the goddess of the hunt, the wilderness, wild animals, the Moon, and chastity.
I left my brother with a lot of grief
Colfer(The author) has said that he based Artemis on his younger brother Donal
Died fiddling with lots of gears
In the seventh book, "The Atlantis Complex", Artemis contracts a mental disease called Atlantis Complex disease, similar to OCD,and has a strange fascination with bivouacking. Artemis finds himself obsessed with the number 5 and fearing the number 4- (which in Chinese sounds like the word for death).
My friends, my friends, cast a lot of tears
The disease worsens throughout the novel, leading to his distrust of his close friends.