I guess I'm a little blown away here, and maybe it's b/c of my youth and limited experience in the workplace - I'm 33 and have been working about 10-12 years.

First of all. . .my question would be if you don't believe you did anything wrong, why did you lie? And the second question would be why did you look up the info in the first place? I guess I'd define "catty" a variety of ways, and it seems like some of your own behavior toward your co worker is somewhat catty.

I think the most important thing is to come clean with someone. If they suspect you looked up the info, then it's b/c someone gave them reason to suspect. At that point, you were only a snoop. If they catch you in the lie, then you become a snoop and a liar. I don't imagine you're going to get out of that too easily.