Couple things here. Firstly; preemptive soaks in preparation for a shed do more harm than good as they rinse off the naturally secreted fluids produced by the snake in preparation for the shed. Soaking should only be done if an entire ring of shed sticks around the snake, and even then some people will say better not to soak at all. The best thing you can do for a coming shed is to keep the humidity levels between 60 and 70%.

As for feeding, do away with the cardboard box. The snake is going to be more curious about a new environment nearly every time and you can expect her to continue to ignore the mouse. Ball pythons don't have much of an aggressive feeding response, and rarely come to associate regular interaction with feeding. Feeding in the enclosure is going to be your best option to spark interest. You also made it sound like you left her and the mouse in the box alone and out of your sight; never do this when feeding live. Her disinterest or a bad wrap could cause the mouse to do some serious damage to her if you aren't there to supervise and intervene if needed. Some of mine eat live, and I'm never more than a step away with the tongs in my hand ready to step in even though it usually isn't needed.