What should you do?
Nothing. You gave her a good time, were pleasant, polite and respectful (I assume).
If she decides another lad is better looking than you and therefore she will dump you to go out with him then I think you have an insight on her personality and you can count yourself lucky that she has gone out of your life. Move on. If she chooses the other guy because she has a better connection with him then bad luck. Move on. If she decides to stick with you than bear this incident in mind for the future and again, move on, this time together.
Good luck.