Add a smile after it. You don't really want to offend her, just let her know you're playing ball with her. add a or whatever. And don't ask her what's up, you don't care what's up. Add a cliffhanger (I have been doing it for a couple of days, I # closed this girl at the library yesterday and kept her hooked with cliffhanger texts)
" your lucky that i texted you because i usually prefer more girly girls :P OMG you're not gonna believe what I discovered today...."