Sam in the movie

Would you happen to know Why Sam is in the Shiloh movie and not the book?

I think that the screenwriter was afraid that if there weren’t more girls in the movie, then girls in the audience wouldn’t like it so much.  But then he shortened the name “Samantha” to “Sam” so that boys would like it more.  But then he had her kiss Marty on the cheek to appeal to girls.  I’m glad I’m not a screenwriter.