Wrong to treat her this way? And what to do now?

Well I guess I should start by saying that there were two girls at work who I fancied. Of the two, one girl was more friendly and ok in terms of looks, the other girl was still friendly but better looking. I went to try my luck with the latter but unfortunately we didn't "click". I guess looks aren't everything...

On Saturday night the other girl posted on her FB page that she now had a boyfriend and changed her relationship status. Not sure why, but I felt like crap after this, I guess she meant more to me than I realised. But on Sunday I had to pop into where she worked, not to see her or talk to her, but to pick up some shopping. And during this brief visit she saw me and said, "Hi, how are you?"

I totally blanked her and walked past her. To be honest I don't know why I did this, I guess it is down to how I was feeling in the sense of choosing the wrong girl to ask out. Anyway, she then said, "Are you ok? Or didn't you hear me?"

She placed a hand on my shoulder and I turned round and said, "I'm fine..." then shrugged her off. She said "You don't sound it, what's up?", then I said off hand "None of your business, leave me alone." She just shook her head and told me "Fine be that way."

Thinking about it now, I am unsure whether I treated her wrong. On the one hand I was unhappy with what had happened, and was trying to protect myself; but on the other hand, she has always been fine with me and was being friendly, and I treated her like crap. So I've got two questions;

Was I wrong to treat her this way?

And what should I do now?

I know I can't change her choice of boyfriend. But I don't know whether to be honest with her as to why I treated her that way, or simply outright lie...