Most of the adjectives describing Ginger are appropriate; however, it may be better to substitute other descriptors for "aggressive," "wild," and "bad tempered."
Ginger is a horse that acts as an example of what can happen to this animal when it is mistreated. Had Ginger been raised in the manner that Black Beauty has, she would be a sanguine horse, as well. But, Ginger was treated brutally when she was young. Ginger was a very high-spirited, not bad-tempered, horse when she was young; because her trainer, who was probably a drinker, was rough with her and did not communicate what it was that he wanted her to do, Ginger felt that he "wanted to wear the spirit out of me" and just make her a dull, obedient horse.
As she relates her history to Beauty, Ginger tells him she was made to wear the bearing rein, which forces the horse to keep its head high in a fashionable pose for pulling carriages. This bearing rein puts the horse into an unnatural position which causes the horse severe pain in its neck. (The argument against the bearing rein is one of the main reasons Anna Sewell wrote her novel; she was strongly against this cruel device along with any cruelty to horses and other animals.)
Because of having to wear this bearing rein, Ginger became difficult because when she was angered and miserable after being mistreated, there was no one to soothe her with kindness; instead, she was struck or given "only a surly word." Therefore, because of this ill-treatment, Ginger grew restless and irritable. (These adjectives are used in Chapter 8) Perhaps, then, these two words would be better than "aggressive" and "wild."