How to let her down gently?

Did You change the idea for the date. What I mean is if You changed it to something she like the she was due to have a better time. I would say go with Your heart. Or You could try one more date with her to see if it was just a one off feeling. If it is not then I suggest telling Her to face at the end of the night. That way she can ask all the questions she needs to with out plugging up Your phone with message. Go with what Your Heart says. Good Luck.