"As soon as Lurveng had heard my story, she became sad."
Translation:lutwIj Qoypu'DI' lurveng, 'IQchoH ghaH.
No. You have identified the reason. In the English sentence, Lurveng is the subject of "heard" and the pronoun "she" is used with "sad". The English version in the exercise introduces the name of the person we are talking about very early in the sentence, but the Klingon version you wrote holds the name of the person until the very end of the sentence. In most situations there is not really much difference between the two, but sometimes it matters. For instance if I were telling a story where you might think I was talking about someone else, but I wanted a surprise ending, I would do it the way you did. But if I was talking about a bunch of people and I wanted you to be clear who I was talking about up front, I'd do it the way this exercise does it. Sometimes, the order makes a difference. So we try to teach you to pay attention to that order in this course so you are prepared for such subtleties when you start speaking with other Klingon speakers.