Post the paragraph or excert that goes with your question and i will gladly help you......
a. the audience knows something the character(s) don't
I guess but crayons always break when I use them
"she" would be the pronoun.
You can rewrite this question as "She is your best friend?"
So in that case, "she" would be the subject.
In English, you just switch around "is" and the subject to make a question and make it sound Englishy
PS in Italian (and probably other languages) you would just say "She is your best friend?"