Why is one of my silkies so big?

I have a silkie hen that is almost the size of a standard. She lays large eggs and has a large walnut comb. She has always been a bigger girl so I was wondering if there is any explanation for this. She’s not a silkie cross and I got her from a hatchery. I like to say that I loved her so much and that’s why she’s big and fat but I would love any other explanations :)