Stop blaming yourself.

Romantic attraction is a strange beast and very uncontrolled. You couldn't control your feelings about this girl - even though she is not interested in you romantically anymore, you still think about her that way even though it would make sense to stop -- so even though it might 'make sense' for her to be interested in you, she isn't.

She may have been interested for a moment, she may not have. Sometimes flirting happens while someone is trying to figure out whether or not they want to take it a step further.

Since this all happened two years ago and she has not contacted you since, it would be better to assume that she is not interested in you at this point.

I also think that Bete Noire's interpretation is right. I have done that when people I thought were friends confessed that they were attracted to me romantically. I really worry about leading people on in those situations.