Ordering chicks and then reselling them is not really any different than what a store does.
Many hatcheries have a minimum order of 15 or 25, or even more chicks. Shipping that many chicks together means their body heat can keep them warm, so they arrive alive and healthy. Shipping fewer chicks...
If she's posting a month in advance, she could be hatching them herself (one week to collect eggs, 3 weeks until they hatch), or she could be ordering chicks and knows that far in advance what the delivery date will be. Either one seems equally possible to me.