Congrats on the three girls and I'm so sorry the little boys didn't make it. I'm not sure why she's digging but I don't think she's actually aware of the puppy that passed away, I mean, as long as she has the three girls to nurse. Hope somebody more experienced than me will answer the question.
In any case I'm so glad mom and girls are doing great. Try and get some rest yourself. I know is the mom who is the most tired but oh boy, is labour a nerve-racking experience for us! It certainly takes a toll on us as well
Post pics as soon as you can and congratulations once again.
Rubi