Well, does she? Her evaluation of the difficulty level could be based on her own calculations, be they correct or faulty, rather than on her being aware of the fact that this simulation's middle name is "No-Win".
As of STII:TWoK, we don't yet learn that the Academy no-win scenario would involve rescuing the Kobayashi Maru every time. That ship is only involved in the scenario we see played out, on Kirk's birthday, and then said to be the one that gave Kirk his first taste of being Superman.
The test in "Thine Own Self", as well as another in "Learning Curve", feature different parameters altogether, but may well serve the same purpose. Although nothing dictates that they should.
No later episode creates ties between no-win and the Kobayashi Maru specs. In the 2009 movie, the ties are of a paranormal sort, i.e. fate and all that - but we still can't tell for sure whether there was a Kobayashi Maru except in the final test where nuKirk cheated, although we can speculate there were Klingons in all the preceding ones, too. That's a test Kirk personally asked to be repeated, though; fellow commander-hopefuls may have tackled the infamous Space Dragon scenario, or the Romulan Surprise Strike one, or whatnot.
In any case, psychological tests are a big thing in the Academy, and can result in a flunking very late in the game, including Merrick's fifth year. No matter how nonsensical the Kobayashi Maru test we see may appear, it probably does serve a purpose, along with a dozen others that do not necessarily much reflect the practical realities of starship command.
Timo Saloniemi