The fact that she's hiding all the time is great! A hiding ball is a happy ball.That means she's settling in. As Dr. Del said, give her about 5 days more to settle in then offer her whatever the breeder was feeding her before. Things should go more smoothly then. If she still refuses, give her 5 more days and try again. Each snake is different. Some will eat right away, others take a little time to feel comfortable.
A baby ball python should be offered prey no smaller than a hopper mouse. Anything else is just too small. Plus, the movement should attract her attention.