Is the word she a concrete noun?

No, the Word she is a pronoun, not a noun. A pronoun is a Word that takes the place of a noun in a sentence. A pronoun can take the place of a concrete or an abstract noun. Examples:

Concrete noun and corresponding pronoun: Janetis my friend, she is from Bermuda.

Abstract noun and corresponding pronoun: Mother Nature can be kind or she can be cruel.