Hi! Welcome to BYC! I have the occasional egg on the ground too. I just pick it up. It's not often, and I don't even know if it's the same hen. You might try putting her in the nest box, if it's the same girl all the time. Put a ceramic egg in there. When she lays on the ground is it in the open or in a dark corner? A dark corner would indicate she wants more privacy, so maybe curtains on the nest boxes. How many chickens do you have and how many nest boxes?