I assume the original intention here was that she loses disposition for every wrong answer, and if you're already under dispo 25 at this point the jig is up and you have to come clean. But the correct lines were given a dispo 25 requirement too. The main issue was that if you started out below 25, the initial dialogue would loop forever. With the later dialogue choices this approach would theoretically work. It would mean that if she hates you, she accuses you of lying even if you give the "correct" answer, which would make sense writing-wise. However, since you can't increase her dispo once you clicked the quest topic once, I don't think this is a good gameplay solution.

So what I did is that if you get every answer right, you pass, no matter your dispo. But with a higher dispo you get an increased tolerance for wrong answers before she sees through you. I think that's a good way to do it.