Hi, I had a similar scenario. I bought 8 laying hens at one time from a farmer when I started my flock last march. I picked them at about 4:30 pm on Sunday. The farmer wanted me to wait that late so they had laid for the day. They were transported in an extra large kennel about an hour back to my place. I needed a couple of things to be finished in my new coop so the hens were in the kennel with food and water until around 7:00pm. I released them into the kennel and in a short time they were roosting. I checked on them around 6:00 am before I went work. They were fine and there were no eggs in the nesting cabinet. When I got home around 8:00 pm a checked the nesting cabinets and much to my surprise there was 9 eggs. Go figure! I only had 8 chickens. LOL. I was told that it was impossible. I'm not a math professor by trade certainly but I can count to 8 and then 9.
The best explanation I got and found reasonibly credible is this and it was from the farmer who sold me the chickens. At certain times chickens go into hyperproduction mode and can actually drop a second egg cell into the egg machine shortly before a finished egg is laid. He figured one of the eight had not laid an egg before I got there. These were all high production reds and quite often laid an egg a day for 7 or 8 days in a row prior to taking a break for a day in the spring time. He said the hen that laid two would have laid the first egg a his place before roost had I not picked them up. With this in mind due to the stress from changing coops and timing she did not lay until sometime early the next morning yet another egg was forming already. It's odd but it can happen however it is genetically impossible I'm told to have a chicken produce two healthy shelled eggs in a single 26 hour cycle.
Some say an egg cell will not drop until provoked by the laying of a complete egg. I tend to agree with this but apparently there are circumstance otherwise. If she continues to lay 2 a day get a go pro mounted in your nesting box and get it on YouTube. You will make millions! Good luck.
Just and FYI , after they laid 9 on Monday, they laid 7 on Tuesday and then laid none until Friday.
After that they started back up with an average of 6 a week each until late July. This in itself lends credence to what the farmer said. The baked all the buns that were already in the proof box Monday and Tuesday and then shut the oven off until Friday when they were comfortable in the new bakery.
