"The Best Day" from Fearless and "Never Grow Up" from Speak Now sound very similar... because they are actually the same story, "The Best Day" from the point of view of Taylor, and "Never Grow Up" from the point of view of her father.
Isn't "The Best Day" about her mother?
Yes, from Swift's POV.
"Love Story" is written as though Swift didn't know how the play ends... neither did Juliet. For all we know, they both die after the song ends. I think it works better that way.
At first I thought "Love Story" was just your typical pop teenage love song. I was always disappointed that she used "Romeo" and "Juliet" for the names of two perfect lovers for obvious reasons and I assumed that she simply Did Not Do the Research... but then I noticed a very subtle change at the bridge. The whole song, she sings to her "Romeo" directly, referring to him as "you". At the bridge though, the precise line is "Is this in my head? I don't know what to think/he knelt to the ground and pulled out a ring..." In other words, the entire climax of the song may very well entirely be in her head, the wistful dreaming of a heartbroken girl, which fits the Romeo and Juliet imagery perfectly. (Also makes more sense of the echo at the end.) Now I hear the song as a bittersweet love that never was, rather than the bubblegum pop love that everyone seems to think it is.
Or the switch to the second person means that her really Romeo, the one who proposed, is someone else, and she's sharing the story with the boy who missed his chance. Never thought about it that way before...
If you want to link it back to the actual Romeo and Juliet, the song could be seen as an alternate ending to Romeo and Juliet, with Juliet narrating to Romeo, where Paris proposes while Romeo is in hiding in Merano and Juliet, tired of waiting for her Romeo to return, accepts.
While not as terrifying as some of the others on this list, "Fifteen" has a small bit of "Wait a minute..." She sings that when you're fifteen, "you're on your very first date and he's got a car." Innocuous at first, until you realize that in most of the US, you only get a learner's permit at 16, and a license actually allowing you to drive a non-family member at 17 or 18, which means her first date might be a significantly older person taking advantage of a younger girl.
There's also places where you can start learning at 15 and a half and drive on your own 16. So not necessarily creepy.
Also, just because you're not legally supposed to drive someone you're not related to at 16, doesn't mean it doesn't happen.
And if he is like 3/4 years older then her, that's not really that much older. I've know girls that dated guys about 5 years older. My mom met my dad at 17, my dad was 24 at the time.