Hi there and welcome to talkbudgies.
So, I'm assuming that Tom/Ruby & Jerry, were in the same cage in the store and they both appeared alert, healthy and chirpy there.
Take a look at this sticky:
Cover the cage leaving just the front uncovered and put on the TV/radio for some low level background noise. Place a shallow dish of water and some millet close to the opening of the box to entice her out. Sit within sight of the box but not right up beside the cage.
To take this long to venture out isn't usual but it IS a big scary world out there, so don't make any sudden movements or noises if she does peep out. If she's young then she might be liking the safety of the box, reminiscing of the security of the nest box, similar to how some young budgies will huddled face in to a corner on the floor of the cage.
If she doesn't venture out within a couple of hours of the above interventions and a calm environment, then I think it is probably wise to gently tip the box to slide her out in order to check that she hasn't hurt herself in some way.
Let us know what happens and we'd love to see some photos when they're more settled into their new home