I don't know if you can use Calcium Lactate or not. Let's ask
@azygous
I do know you can use Calcium Citrate.
Is her crop empty first thing in the morning before she eats/drinks? If it's staying fully and squishy, I would treat for Sour Crop according to this article
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/
Getting Calcium into her is a good idea as well, she may be having problems with another soft shelled egg. It's possible that she has laid internally as previously suggested in the other posts.