I think we're seeing the evolution of Jeph's art here, and not any kind of intentional change in appearance.
In the 400s, the differences in characters were pretty subtle. I think Veronica looks youngest in that series, if only because her appearance isn't that different from much younger girls and she almost looks like just a
slightly larger Dora.
The 1800s show a pretty big difference between the beginning and end. When she appears in
1820 the lines defining her cheeks and eye lines are pretty dark, making her look much older than in the 400s... so much so that I was trying to figure out who she was. By
1829-
30-
31 those lines have significantly lightened and are much more subtle. Were I guessing I'd say Jeph was figuring out how to draw her in the updated style and made some adjustments along the way to dial her in a little better.
At the wedding, for me, anyway, the glasses really dominated her features. The cheek lines are now gone, eye lines remain and are more shading differences than actual lines. You could convince me that perhaps she had some work done in between to soften those cheek lines but I think it's just as likely a drawing style update.
So take her glasses off and return her to her home setting in relaxed mode and you get the hotness that is
2484. When I get a chance to watch the stream (which I highly recommend... watch Jeph's twitter each night for details and a link to the stream) I'm frequently astonished how much difference the glasses make. He draws the faces first, then adds the glasses later.
If I get some time I might put together one of those side-by-side-by-side multi-frame pictures of Veronica's appearances (if no one beats me to it, hint hint)