"What's wrong with talking about something known as the 'Grand Betrayal?' I get that it's a terrible thing to happen, but its not as if avoiding uttering the name will magically will it into being or anything like that."
The Grand Betrayal was the third of the five key events. According to the tome, the Grand Betrayal would come some time after the first two. Given the civil war in Merthin, Tess knew that it was entirely possible that the first condition of the Night Tome, the attack on a single nation, was already fulfilled. Caleveh's emergence was also possibly a part of the second condition. These two things together made her wonder if the Grand Betrayal would happen sooner rather than later.
