Describe Ginger’s mistreatment by her owners prior to coming to Bertwick Park and the change in her behavior after coming to Bertwick Park.

Black Beauty relates the tale of when he lived with Squire Gordon at Birtwick Park. When the young colt arrives at his new home, he's led by the groom into a loose box, so-called because the horse that's put into it isn't tied up and is left loose to do as he pleases. At first, all seems well. Black Beauty's given some nice oats to eat, and then meets a kindly gray pony by the name of Merrylegs.
But the pleasant atmosphere doesn't last for long. A tall chestnut mare called Ginger gives Black Beauty a piece of her mind. It's her box he's standing in, and she doesn't like it one little bit. She thinks it's outrageous that a young colt should turn a fine lady horse like her out of her own home. Black Beauty points out that he's done no such thing; he was put in Ginger's box by a man. He tries to placate Ginger, but it's clear that he's going to have more than a little trouble with this proud, pompous mare.
After Ginger goes out for the afternoon, Merrylegs tells Black Beauty all about her. Apparently, Ginger has a bad habit of snapping and biting; that's why the stable hands removed her from the loose-box and put Black Beauty in there instead. Ginger's quite a violent horse; and after she bit James the stable boy, Squire Gordon's children became too scared to go anywhere near the stables. Merrylegs says that Ginger told her that she'd been treated very badly before she arrived at Birtwick Park; this would account for the nasty biting habit that she's developed.
Later on, Ginger opens up to Black Beauty about the appalling treatment she's received in the past. Since being taken from her mother at an early age, and forced to mix with a lot of young colts, she's never been cared for by any horse or man. With her wild, noble spirit, Ginger deeply resented being treated as nothing more than a piece of horseflesh by Samson, the son of one of her previous owners, Mr. Ryder. As well as being an alcoholic, Samson was also very cruel, and used to run poor Ginger ragged, making her run around the training field all day. If Ginger ever refused to do as he asked, Samson would subject her to brutal physical punishments, using whips and spurs. Thankfully, Samson's old man took over the reins and Ginger was able to receive proper training. But by then, the damage had been done, and from then on, Ginger's instinctive reaction is to lash out at anyone she perceives as a threat.
After being broken in, Ginger worked as a coach-horse for a fashionable gentlemen. But she hated the work; the cruel check-rein that was used on her caused considerable pain and restricted her movement, a serious problem for such a free-spirited horse. But Ginger's master couldn't care less; all he wanted was a fancy horse that looked good; he never once thought of Ginger's welfare. Ginger responded by kicking herself clear of the harness and so ended up being sold; that's how she wound up at Squire Gordon's stables. Kicking is clearly an instinctive expression of Ginger's desire for freedom, and it makes her rather difficult to handle.
On the whole, things are much better for Ginger at Birtwick Park. Here she receives much more kindness and understanding. But because of all that she's been through in the past, all the cruelty she's had to endure, she will never fully be able to trust another human being as long as she lives.