How to move on

So let me start off my story with the background. I had a secret crush on this girl who of course was very pretty. I was about 13 when it first happened and we spoke and joked around but nothing serious. Never really spoke to her much in high school. Then it turns out we both went to the same college. I saw here there freshman year and we started to talk again. Eventually we started studying together. It didn't help matters that we got along so well and people used to say they never saw her laugh as much as she was with me. It was also a strange thing as well as she never really talked about her personal side. It came down to the point where I was always helping her, but she kinda kept pushing me away. Finally on my 21st birthday I invited her to my party and she made some weird comment that she didn't want people to know she knew me. I snapped at her and she never spoke to me again. Two years later we ended up interning at the same company and we got into a fight which surprisingly we ended up making a sort of peace out of in the end.

Fast forward again and I actually asked her to dinner since I am now in a sales job and the company she works for is one of my customers. So I thought it would be a good idea to make sure everything was still cool between us. The strange part is during the dinner she asked if I was seeing anybody and I told her no not at the moment. Then randomly she brings up the statement that her boyfriend would really like me. Now I am going oh great I went from making peace to becoming creepy. My question is what do I do now if I see her through my job?

I don't see how you are "creepy"... if she thought you were creepy, I doubt she would have had dinner with you. When you see her at work, just casually say hello, how are you? She's already involved with someone, so you need not over-think this.

I guess you are right, but the one time I saw her after that she sort of ignored me. It doesn't help that she is a bit odd too. She always got a lot of attention when we were younger so she I think it went a bit to her head. Here is the stranger part she ignores me then adds me on Facebook a few weeks later.