He wrote "Tell Her" for Katie, and I KNOW he wrote "She's No You" about her, since after all, she IS featured in that music video.
Another thing I noticed when my sister and I were watching his "It's Over" video, is on the part where he sings "So when you call I'm pressin' 7, don't wanna hear your messages (messages), I'm tryin' to erase you from my mind" he is looking at a cellphone and it specifically says on it "Calling....Katie."
At first I was thinking "Did I JUST see that?" but it sure was, because we rewound it and paused it and it WAS on there.
If you don't believe me, check out the video for yourself. I hope I helped and its so nice to see another Jesse fan like myself on here. :)