There was this girl that sat next to me and I made a few jokes that made her giggle alittle bit... later that day she came up to me and I pretended not to know who she was ..........
Just means your a snobbish person, thats all... Don't worry about it there are plently in this world.
maybe you sensed instinctively that she's not your sort, and you didn't want her to get the wrong impression because you're currently unavailable (for whatever reason), and doing it this way, with a little "pretend" is better than stringing her along and hurting her feelings later. so, really, you did her a kindness by not allowing her to invest time and emotion into a relationship (even if just friendship) that wasn't going to work out anyway. good work. this way, if you change your mind, you can approach her gently later.
having been on the receiving end of the "blow off" many times, i know i've been greatful that someone decided not to let me waste time and effort.