There's a saying that goes alongisde the lines of: "The future changes by merely looking at it." Knowledge of the future and whatever may come towards us pays a great deal on the unfolding of its actions.
The elf's statement of "never getting a single prediction right" could be interpreted alongside the lines of "I get a right prediction of what was going to happen, but my clients changed the outcome so the predictions never ended up coming to pass". Why am I making such an assumption? Because most of us can agree that what the eroelf said hit quiiiite close to home and looked liek a pretty realistic depiction of, not only what could have happened, but what a great deal of people here in the forums say ought to happen not only in this manga but with tsunderes in general. Hopefully the weight of the knowledge will make the knight change her attitude and make some progress with the relationship (because she may deny it all she wants to but we all know they're pretty much a couple already).
But then again, the mystic woman could have simply done a cold reading on our tsundere muscles and played her like a fiddle, you never know with these dark elves.