I have heard so many stories of a guy getting rejected, even multiple times by a girl and then taking it in stride. He keeps coming back, but in a confident, secure way. Not in a desperate, needy way (there is a HUGE difference). Eventually they end up dating.
Like someone said, go about your normal routine. Pretend like it never happened and do not let it get you down. She made a mistake. Girls honesty know sh1t about what they really want in the end and what is good for them. The fact that they can reject a guy and then fall in love with him is proof of this fact.
Internalize this attitude that she made a mistake and is missing out. You are trying to help HER by getting her to date you. She may stray, but stay strong.
You need real, internal confidence to pull this off. If you're still faking it at this point, you will eventually crash and burn, be warned. I have experienced crash and burning and I have experienced success (where I am at now I honestly believe this stuff and have internalized it to the point that it is natural).
peace