With deference to her royal heiness, the Princess Frances, does she (or anyone else here) have any issues with the characterizations of Lucy, Susan, Polly, Jill, or Aravis in any of their books outside of TLB? Do you feel any of their dialogue was out of place? Should the respectable Mr Lewis have collaborated with other females in his life when writing those main female characters?
What of other authors? Rowling was a female author who wrote a series of books through the voice of a 11-17-year-old boy. Many authors have written books in the voice of characters opposite their own sex, notably the classic Anna Karenina by Tolstoy.
Characters can be extremely personal extensions of the author and only they can understand that character's personality. People in real life are so varied and different that the reader can understand that this character is just different.
MrBob