Well... You really fucked things up by saying that haha, but there's hope on the horizon! Supposing she was sincere, the fact that she showed disappointment with your response, means:
1. She is actually hurt by your response, but if you play it off right you can turn that sadness into a stronger, smarter relationship.
2. She was fishing for compliments, and got disappointed by your response (haha) and you can probably fix that one up too.
3. She was doing a terrible job of getting you to say something incriminating so she could break up with you? But you fell for it... haha I don't know the girl but it's what my friend did to his girlfriend hahaha.
You can play this off smooth by saying you made a mistake, and then do what skiierman said.