Am I flirting? Need Opinions Please.?

[SSike]

So, I was engaged in some friendly banter with a girl on twitter recently, (I tweet a lot, not just girls, but this one caught the attention of my wife because of the length of conversation) and my wife wanted to look at it, to which I happily obliged, thinking that there was nothing sinister in the conversations that I had. She saw a passage of writing that led her to think I was flirting with this girl, and I strongly disagree with her, so now I'm asking if people could tell me what their opinion is with the following dialogue:

HER: "And just as a matter of clarification: I use sarcasm when I want to be nice. Is that a contradiction in terms?"

ME: "Not a contradiction. Like the boy at school who is meanest to the girl he likes. Now just to figure out when you're sarcastic"

My wife says I'm flirting, but I felt I was merely making a comment analogous to hers about contradictions, and that was the first thing I could come up with. My wife however, thinks that I was subtly saying that I liked her.

Someone please help. I'm willing to admit I am wrong if I am, but I just don't see it.
@Chattu - Thank you for your reply. That definitely helps to hear this coming from another girl. I guess the important thing is to make sure she knows exactly how I feel about her, then talking to other people won't be so bad.
@Ron - I appreciate the insight. I think it's not so much that she thinks I am flirting with others, but that she thinks that those other people will think I'm flirting with them, and that results in her feeling foolish/disrespected.