Here's why:
* Comparison: The sentence is comparing the performance of "she" to the performance of "you."
* Than: The word "than" introduces the second element in the comparison.
* Pronoun Case: After "than," we use the objective case of the pronoun, which is "you" in this instance. The subjective case ("she") is used when the pronoun is the subject of the verb, and the objective case ("you") is used when the pronoun is the object of a verb or preposition.
Let me know if you have any more grammar questions!