If she took time out to respond, she wouldn't have any time left to act. I, for one, would prefer it if she could keep acting. I don't think fans got her where she wants to be. Bankability gets her movies like Pirates, whereas talent gets her Atonement and Pride & Prejudice.
She owes us nothing. We buy tickets to her movies because we choose to. She's probably struggling to balance her acting life with her private life, the last thing I wish for her to have is less of a life because she's busy writing letters to people she knows nothing about.