Nutmeg Tiger had thought Black Sapphire was a bad omen once he had arrived unannounced in the spicy lands... Until she had seen that he, Candy Apple, and his "beloved" master were injured and weak, apparently having been semi-defeated by their counterpart a bit after Burning Spice had been.
Although ruins were all that was left, Black Sapphire insisted that they had nowhere else to go. She was suspicious, and with Burning Spice out of commission for the time being, she had a say in it all... And yet, she reluctantly let them stay under the condition that the three wouldn't dare try any funny business.
Black Sapphire promised that nothing of the sort would happen, but Nutmeg Tiger would never really trust a liar. Somebody would have to keep an eye on the three during their stay, and what other cookie could do it than her? There was no way in their weakened state that they could go against her!
Not like she would've admitted it at all, but it was... Nice to be around other Cookies after the defeat. Maybe Black Sapphire reluctantly knew the truth of that within her. Maybe he was playing along in her denial.
Maybe he was playing along with his own.