First of all, congrats on your new chick!
To answer your first question, yes, she will lay again. It will take a few weeks, but then she'll get back into her usual laying schedule.
Your hen will most likely go broody again. That just gives you an excuse to hatch more chicks!
The mom and the baby will not form their own flock. At first, the baby will always stay by mom, and they will always be together. Then, when the baby gets a little older, she'll start wandering farther from mom, and be more independent. Eventually, when the chick is a few weeks old, the mom will stop sleeping in the nest box with her. Then, when the baby is about 2-3 months old, the mom will completely separate herself from the baby. Sometimes, this separation can be kind of brutal, because the mama hen might peck the chick to tell her to go away. Finally, the baby and the mom will separate, and the baby will become a member of the flock like her mom. The mom will go back to her usual self.