"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?"
Setting is the time, place, and circumstances in which something takes place
A metaphor compares two unlike things without using 'like' or 'as'. Example: Happiness is a warm puppy. Happiness (an abstract concept) is being compared to a puppy (a physical object).
