I guess it would depend on what they were started on. If started on some drawn comb or one of the fully drawn plastic frames she could begin laying quickly. If they were started on foundation, they will have to draw out some cells for her to lay in. Sometimes a colony can draw out a full frame in a couple of days if they need it. As an example, I hived a feral swarm a week ago and in 9 days they have drawn 9 complete frames (NO foundation/starter strips etc.., just their own wax and one partially drawn frame for a starter). If it will give you some piece of mind, take a quick peek at the center frame..... Still wouldn't count her as gone until a good week had passed as it can take a coupld of days for her to simply settle down and get to work. A downside you should be aware of, a colony just starting out can be a little jumpy.....Since they haven't established your box as their home, too much disturbance could prompt the whole colony to abscond. One thing you can do right now- observe the activity at the hive entrance for bees with loaded pollen baskets. Pollen baskets (while not a sure bet) are a good indication that they either have brood or they are expecting brood soon. Remember, bees are bugs and don't spend alot of time reading the books that tell them what they are supposed to do.