As an employee, Joanna could mind the store in Su Ping's stead.
For example, receiving customers and collecting fees.
As for pet training—
Joanna was not allowed to go to the cultivation site by herself. Su Ping had to be the one taking her there.
That being said, Joanna could help Su Ping use the dummy trainer.
Su Ping just needed to pick out the cultivation sites for the dummy training before he left. Joanna could pick out battle pets from the storage space and put new ones in.
That way, when Su Ping was away, Joanna could still keep the store running.
Even though she would only be able to finish the general training, making some money was better than making no money.
Su Ping told Joanna everything she needed to know. Then, he looked at Tang Ruyan. This time, he didn't send her back into the scroll. Joanna would be too busy on her own.
"Remember to help Joanna out," Su Ping said to Tang Ruyan.