I agree, that is probably her!So I caught her in the nesting box just hanging out and I waited for like two hours and she came out and there was an egg that hasn’t been there prior. She has done that twice now so I’m confident it’s her.
I'm pretty sure they are all femaleThey are pretty young. Around 18 weeks and none of them have crowed. They all play and chase one another too. It’s four of them. I’ve attached some more photos of them

So to answer the question in the title of the thread-- no fertilized egg, regardless of how it looks.