Help me I didn't reject someone but emotionally I feel horrible. :(?

I didn't reject this girl but I feel horrible. My situation began when I started talking to this girl about a year ago as friend then later I am not sure how we progressed; she became closer to me we called each other more often etc. But, as of late we had not engaged in conversation so I didn't know what to think and I ended up going out with this really awesome girl but now I am in so my pain possibly because I empathize way too much or maybe its because she is infuriated. What should I do?