The timing here is not good. Hatchery chicks have already exceeded their three day window from hatch, and need to be fed and watered often. When a hen hatches eggs, she waits on the nest for 3 days after the first chick hatches and then takes all the hatched chicks to get water and food. Anyone left unhatched at the end of those 3 days is usually abandoned and dies. So if you are putting hatchery chicks under a hen that hasn't even hatched her own eggs yet, they need to eat immediately - they may starve/die of thirst while she sits on the nest for three days waiting for the rest of the eggs to hatch. Or she may get off the nest, leaving her own eggs to die. Either way, the chicks will be a week or two apart once eggs finally hatch, which is not good for the smaller ones.
I would not introduce these hatchery chicks to the broody, but would raise them in a brooder. They can be introduced when the youngest chicks are 4 wks old. I would let the broody raise whatever she can. Unless you stick hatchery chicks under the broody immediately when they get home (after they've had food and water once they get home with you) and she's ready to take them off the nest right away, this is not a good situation.
The eggs will hatch starting Sunday through at least Tuesday. So by the time the eggs have finished hatching the hatchery chicks may be 1-2 weeks old. I would not mix the chicks.
In future, if you want her to adopt hatchery chicks, have her sit on dummy eggs, then remove them and replace with hatchery chicks. Once eggs are gone, she's more likely to take them out to eat. You'll need to watch and be sure she doesn't reject the chicks and that she takes them for food and water that day. They have to be very young from the store. Or you can slip a few hatchery chicks under her once she's just finished hatching hers and see how it goes, but either outcome is uncertain. It's a try it and see approach, and depends on the individual hen whether she'll adopt them or attack them.
