Perhaps Alistair's words reached her ears, or she already had a plan from the beginning. After all, a good knightess always has a backup plan. In war, things are often unpredictable. No one knows what could happen one moment from the next.
As such, Sierra had learned to not rely on the first plan she concocted. She always had something brewing at the back of her mind, just in case. This situation was no different. Upon realizing she could not rely on the largest catch from the hunt, she immediately changed her strategy to focus on one of the three types of herds she could hunt.
A herd was a lot more difficult to stalk at times, especially on horseback. As such, Sierra kept Midnight in a cave and told her mare not to go anywhere.
"I will call for you at the opportune moment," she whispered to her horse.