DB, reading that made me think I was reading an interaction between two 15 year olds.
Lose the emoticon's and 'Haha's it's girly, gay or makes you look uncertain about what you are texting. If you send something that you mean as a joke but could also be misconstrued as you being serious then for me that's even better, don't reassure her by adding smiley faces allow her to think 'Is he being serious or joking?' it's about being intriguing. If she doesn't respond don't cave in and say 'I was only joking' etc.

Be self-amused by your own humour, if she doesn't get it, that's not your problem.

Definately try to talk in statements rather than asking questions, if she's asking questions then by all means answer them if you find them of interest to you, if theyre boring questions I don't bother i'll move on to talking about something else.

I think making references to her about being on a 'leash' or generally just being a dominated women unable to think and act with free-will isn't something you should poke fun at or make snide remarks about. Some can get quite sensitive about that, they all like to think they possess some kind of 'girl power' no matter how weak it really is. You'll get a more favorable response by treating her as an independant women capable of making her own decisions and respecting her boundaries, even if in reality she's not really like this.

Persisting with girls who have boyfriends is fucking lame, please don't do it. You wouldn't want the same to happen to you.

You say you've known this girl for some years, she became a bit of a oneitis for you. I don't think you're fully cured, rather than beating yourself up about it, seriously - move on.