How does Ginger die?

In Anna Sewell's classic novel Black Beauty, Ginger is Black Beauty's friend. She is a chestnut mare with bad manners. She has a tendency to kick or bite. Black Beauty and Ginger meet at Birtwick Park, where they have very kind owners. Merrylegs, the pony, speculates that Ginger has bad treatment before she comes to Birtwick Park and that is why she snaps and bites people. Beauty and Ginger are paired together to pull the carriage.
After a time, Black Beauty and Ginger are separated. In the chapter entitled "Poor Ginger," Black Beauty sees Ginger again but doesn't recognize her. When he sees her, she is in London pulling a cab. She has a bad cough. Most of her ribs are showing. She has swollen joints and is unable to lift her head very far.
The life of a London cab horse could be quite brutal. They were often expected to carry loads heavier than they should have been asked to carry. They were exposed to the elements and worked for long hours. They often didn't get enough rest or proper medical care. Horse teeth can develop sharp points or "hooks" on them, and if their teeth are not "floated" yearly (a process in which a veterinarian takes a file and smooths out the sharp points) horses can have a very difficult time eating. This is one possible reason Ginger has lost so much weight when Beauty sees her again. She tells Beauty that she wishes to die because she has lost all hope in life and has been treated so brutally. In the quote below, Beauty describes seeing her for the last time:

A short time after this a cart with a dead horse in it passed our cab-stand. The head hung out of the cart-tail, the lifeless tongue was slowly dropping with blood; and the sunken eyes! but I can't speak of them, the sight was too dreadful. It was a chestnut horse with a long, thin neck. I saw a white streak down the forehead. I believe it was Ginger; I hoped it was, for then her troubles would be over. Oh! if men were more merciful they would shoot us before we came to such misery.

Ginger dies from neglect, maltreatment, and losing the will to live.