Translation:That pretty girl is not thinking about him.
You have asked the same question, and, believe it or not, the answer is the same: In this DL course, the Czech demonstrative adjective (to, ty, etc.) is translated either as 'the' or 'that', but not 'this'.
Furthermore, if there is no demonstrative adjective in the original Czech sentence, then the word 'the' is not arbitrarily inserted into the English translation. (The indefinite article 'a' may be used instead.)
This DL course is quite consistent on this point. Please convey my best wishes to your teacher, even though his point of view is not adopted in this course.