Welcome to BYC ! It is completely normal, Chickens just lay where they want to at first. You can place 3 or 4 golf balls where you want her to lay and it will encourage her to lay there. Give her time and she will come around! :)
This looks to me like infected sinuses/ respiratory issues, I would treat with a sulfa drug like sulmet that you give in the water. Is there any discharge from the nose? Does she wheeze, sneeze, or anything similar? Do you have her separated from the rest of your flock?
The weather could have an effect on her, since droppings and everything seem normal I would start with giving her electrolytes and vitamins, polyvisol is a good one or you could give her childrens pedialyte. Is her comb and wattles bright like they normally are? this is where I would start. Hope...
Personally I use shavings, but most people I have run across recommend using sand... I tried to look up your question about EVA, but couldn't find anything hopefully someone can help you with that. Welcome to BYC!!! glad you joined us!