Answer:
She is implying that the works she writes are not intended for a specific ethnicity or person, just like the works of C.S.Lewis.
Explanation:
Kamila Shamsie is an ethnic Pakistani writer. To make it clear that her works are not aimed at the Pakistani community, nor any other specific ethnicity or race, she compares herself to C.S.Lewis. In this comparison she claims that Lewis probably did not write for a girl, she specifies, in Karachi, but wrote global works that reached people of different ethnicities and cultures, just like her.
