Abish had already been converted, so the overwhelming transformational power of the spirit did not overcome her. She is able, therefore, to understand what is happening. Even with her conversion, what let her know what was happening with so many people? Certainly the spirit was with her, but she had also been there when the king, who had been as dead for two days and two nights arose from his bed. Thus she had a very immediate understanding of what had happened, and the awakening of the king, for however briefly, would have given her the confidence needed to declare what would happen in this case.
Textual: As a more personal note, we are told that Abish did not make her conversion known prior to this time. This suggests both that she understood that it would be dangerous, or at least difficult for her current position. These were Lamanites, and they would not have taken kindly to a servant in the royal court who contradicted the official beliefs of the court. The fact that we have this piece of information also indicates again the probability that there was a much longer story of Abish available, so that Mormon would have access to these details, and consider them of sufficient interest to include them.