It's also an abstract question. I answered one on here yesterday about a guy tapping a girl on the shoulder and I'll say the same thing: things like this can't possibly be analyzed enough to find any meaning in them. Don't stress yourself over something so small and instead find real ways of knowing if this girl likes you or not.
Yeah dude, I'm sorry but you really have to post more than she just used a winky face. And really, reading into one winky face is too extreme. You need to look at the whole picture, all her texts and body language and the way she talks to you, you'll be much better off than analyzing one small winky.
Heck, I just saw a Facebook status about a friend of mine who accidentally sent a winky when she meant to just send a smiley. Imagine that was you and now you're reading too much into it!