kmy,
Try not to slam your friend too much. The Adcom obviously saw things they like in her. Maybe what you see as "flaky", they see as humor. Maybe what you see as "a lack of dedication", they see as well-roundedness or something. You just don't know! Further, remember there are a lot of things that go into "when" you hear something back from a school. For instance, if your file is reviewed by individuals before it goes to committee, maybe her "individuals" got her file done right away, while yours are slower and left your file on a desk for a while. Again, you just don't know.
That being said, it's PERFECTLY OK to be jealous of your friend! It's even OK to tell her you're jealous. Just make a joke of it, as in "AGH! I'm soooo jealous! get out of my sight, you! (ha ha ha)". Everyone gets driven a bit batty by this process, so don't be too hard on yourself, but try not to be too hard on your friend either. And don't murder her. That would be BAD.