OP,

Nothing in your initial post signified a bad attitude, or inappropriate reaction, really. Is it possible that you missed something? (Like that she had just walked through the aisle 15 seconds before with bottles of water.)

Or is it possible that she simply smiled and did as you asked without any verbal response because none was needed?

I only ask because you said that the pilot looked at you funny as well. Which makes me believe that either 1) you did do something a little weird (and I don't think asking for water in first class would qualify) or 2) your perception might have been off. No offense intended.