The Demon Fox Race's current sanctuary was safe only because the Fox King was using all her power to maintain the Grand Array. Her ability was the sole reason such a vast space could remain hidden.
If her cultivation hadn't reached the Void Spirit Stage, she would have found it impossible to maintain the array for so long. More importantly, she was seriously injured, which explained her pale complexion. Injuries sustained by experts are often harder to heal. It's not that they recover slowly, but that the wounds they receive are typically far more severe.
With such grievous wounds, her injuries were naturally severe, making recovery difficult. The fact that she was also maintaining the Grand Array certainly slowed her healing even further. While the array could function without her, its effects would be greatly diminished, and they would be discovered easily.
