Correct Answer: C
Explanation:
Replace ‘she saw me before’ with ‘she had seen me before’. Before is qualified by ‘Perfect Tense’. Here the sentence begins in Past Indefinite Tense, hence ‘before’ will take ‘Past Perfect Tense’ with it.
Moreover, in case of two activities of the past, the one occurred earlier takes ‘Past Perfect Tense’.
Hence option C has the error.