Thank you so much!Hi, Welcome to BYC! I would remove the eggs, she will not lay another clutch until those eggs are gone. Make sure you are at a safe distance when you smash them. This happens to them in the wild when a coon gets the eggs, most often they will lay another clutch. I have had my mallards lay three clutches in one season.
That’s what I’ve been hoping, but it seems she is determined to keep going.
I would remove her from the nest and break her broodiness.
Thanks! I did notice that one egg has a crack line today, but I don’t know if it’s new. I’m going to give it one last day and if no ducklings hatch, I’ll remove the eggs tomorrow morning. So sad!
Hello and welcome to BYC. You found an Amazing Poultry Community to be a part of, with many knowledgeable members who are willing to help you along your journey with any questions you may have. Enjoy 
I would have to guess she went broody and her eggs were not fertile. I am curious, have you seen any drakes and or other ducks around your area?Hello! Yes, there are many mallards in a pond behind our backyard. I watched a drake follow her into our yard this week when she returned from feeding. It’s the only time she’s ever made a noise. He came back several times during the day, but she stayed on her nest. Haven’t seen him since. As for the eggs being fertile, I’m pretty sure they were. Last week I found one in the bottom of the pool and there was definitely a duckling inside.
Thanks for sharing your very interesting story with pics.
Me too!!!That is interesting, she sounds like a good broody hen. I wonder why her eggs didn't hatch on time?
Personally I would remove the eggs. 
