Maybe you could try and be a little more edgy and daring. Just have fun with it when you are texting, I mean if you play it conservatively because you're worried you won't see her again if you screw up then you probably won't see her again.
If you probably won't see her again then you may as well go for broke.
Here is a recent example from my phone.
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Me: So what kind of mischief u getting up to tonite?
Her: Haha mischief... I spent the day getting (*lifted*) for the first time in years and baking cupcakes. Has completely destroyed my motivation, was meant to go out tonite but cbf. You?
Me: I think we just having drinks at the new place. Im waiting on a friend, if its cool with her we can pick you up on the way...
Her: I am so close to passing out ;p Got mates swinging by for dinner then will get an early night I think! If the weather is ok I might hit the gym tomorrow or go for a run to make the most of a non hangover sunday! New place?
Me: Lightweight lol. I might get (*lifted*) myself, damn shame I probly shouldnt hav invited u tonite then coz if you keep saying no I'll lose interest ;p I just saw something that reminded me of u heheh
Her: I already bailed on plans tonite. I am so silly. This is why I dont smoke! Im meant to be at the Scotto by now!! What did u see?
Me: Haha true it was kinda an impulse invite lol well if u really wanna know I saw a pornstar with an awesome fake rack so naturally I thought of u ;p
Her: Hahahaha of course. R said he and D were debating if they were real or not. I assumed it was common knowledge ;p
Me: Nope your body is a myster to many I should really give u a 'hands on' appraisal, collect some 'hard' evidence and solve this mystery. Its for the greater good.
Her: You Dork ;p
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So you see even though I got a no almost immediately I didn't quit and turned it into something fun and a little risque and even had her qualifying herself to me.
That was a couple of weeks ago and I've been too busy meeting other girls to have time to ask her out again plus thanks to facebook she's likely seen pictures of me having fun with different girls so I'm pretty confident that next time I do ask her out she'll be less likely to say no.
Try to push the boundaries a little more and have fun with txt game, even if you don't get a date you can still maintain or even increase her attraction to you.