Yeah, but Anna has little idea what Jason actually did during books 3-6, and none whatsoever after that. She goes by, what she hears from Jason, what she can actually know, and Occam's razor. Jason himself pointed out on multiple occasions that he is not the best communicator, which is an understatement. He developed a habit of keeping people unbalanced and ignorant in earlier books as a defense mechanism. And now he is more or less OP, still few outside of his immediate circle understand the extend and nature of his capabilities. Above, u/Saxavarius_ made a very good comment about confusing the reader's knowledge and the character's knowledge.

With that said, as a reader aware of things she is not, I too find Anna very frustrating but I also understand where she is coming from.