Zoe is one of my all time favorite female characters in any show ever... her warmth, humor, sexiness, and rock solid dependability were human and believable because Gina embodied all of that so well (I got to meet her at a convention and she is so funny and quick to open up and connect with people... and had a game going with Adam 'Jayne' Baldwin of which of them could get louder applause from the crowd).
And like you I was more destroyed by Zoe's reaction to Wash's death than I was to his death itself... I was sobbing into my coat (that I was holding on my lap) as she gave up all hope and saw just a suicide mission ahead of her.
*sob*