Are Mollie's actions in the Battle of Cowshed justifiable?

During the Battle of the Cowshed, the humans under Mr. Jones try to take back the farm from the animals. As led by Snowball, the various animals launch their defenses using their individual strengths. Although the animals do finally repel the invaders, the men shoot and injure some animals.
Mollie, a horse, had pulled Mr. Jones's cart when he still ran the farm. He spoiled her with sugar cubes, and she wore ribbons braided into her mane.
Mollie does not handle the post-rebellion situation well. Missing her old, easier life, she shirks her new work, breaks the rules, and spaces out gazing at her own reflection.
During the battle, as the fighting intensifies, Mollie does not participate but instead she hides in her stall. She is the only animal that did not fight.
Whether her actions are justified depends on the reader's sympathy with the animals as a group and with each specific animal individually. Orwell presents Mollie in a very negative light, as selfish, shallow, and vain. She had been coddled and largely spared from animal-life's hardships. In her cowardice and weakness, Mollie is contrasted to another horse, Boxer, who is brave and strong.
While Mollie's actions could easily be condemned, it seems unlikely she would have contributed much to the battle. Certainly nothing in her previous life prepared her to be a fighter. Rather, her whole upbringing encouraged her to want to be pampered once more, and that is the path she chooses: to return to the humans. Survival to her did not involve solidarity with the other animals, and by the time the battle even started, she had long ago become detached from the concept of self-respect.