"But she will have to join my army. Otherwise, you can forget it." Minos said, just so he and Vivian could hear. "I don't do charity."
Obviously, they were talking about Grace, who was right behind Vivian on White's back. As for what Davy's sister had asked Minos, well, that was for this young man to give her girlfriend a chance to learn the army techniques.
But Minos would not do such a thing without motivation. What would he get out of it if Grace got stronger but had no obligation to help him?
It would be foolish to do something like that!
As such, he had promptly told Vivian what would be the only possibility for Grace to take advantage of chances similar to the ones she would have.