"Ella afirma que no bebió vino."
Translation:She affirms that she did not drink wine.
I think of "confirm" as a response to a question, theory, etc. "He confirmed my suspicions." Affirm indicates more of a statement and is less commonly used.
affirm = to testify, to swear to, to declare and confirm = to verify, to establish as true. Sometimes pretty much the same, sometimes not.