So she started laying this past summer, was a regular layer, and has now skipped three days. That's not what I'd call a new layer. And you are in Florida, the northern hemisphere. Mild weather. That eliminates a lot of things and points certain ways.
My first thought is the molt. Some pullets skip the molt their first fall/winter and keep laying throughout the winter. But some doesn't mean all. Are you seeing feathers floating around, that's sometimes the best way to tell? Molting generally starts at the head and works its way down the body.
I'll mention hiding a nest again. This is really common when we think they have quit laying.
I'll mention that some critter could be taking them but with others laying it's unlikely they would only take hers. I take it you are not finding evidence like bits of egg shell or wet spots in the nest. In Florida the typical critters that take an egg without leaving a trace are snakes, canines, and humans. A snake typically takes a few eggs, then goes off to digest them before coming back for more. I guess it is possible but a snake just doesn't feel right.
A fox or coyote will eat eggs but are more likely to be interested in your chickens. Probably not them. But a dog can eat eggs without harming the hens. Does a dog have access?
A human doesn't necessarily mean a stranger or a thief. Some people consider something like this a practical joke. That's happened more than once on here.
It's possible she is cutting back because of the shorter days but I'd consider it unlikely.
There are some diseases that could interfere with laying but as long as they are acting healthy this is unlikely.
To me it is most likely the molt but hiding a nest is still on the radar.
As for the small egg, if it is one off it is just a glitch. It may not even have a yolk when you crack it. Stuff like that happens. If it occurs regularly then something is going on, but I don't worry about an occasional glitch.