ow. That sucks. I can't imagine why she'd be /angry/ at you, though. 5 hours on the phone, 3 hours in the park, sounds like you had this one in the bag.
For future references, DO NOT directly answer questions like the one she asked you. In that case, you should've said, "I don't know, it'll take a few dates before I can decide." By spelling out your feelings for her in that message, you sabotaged a very important quality. Many girls love the chase, and if you just give yourself up by admitting your feelings so early, it kills attraction very quickly.