Not sure if that could have killed her or not, I guess it's possible that lifting her may have caused the babies to shift inside her and made it impossible to deliver. I don't move my females at all and leave the whole colony together for their entire lives but I've still lost some pregnant ones from time to time. I think giving birth, especially for a first time mother is just tough on them.

I also like to use a brown male and white females for my mouse colonies. It makes it easy to find the male right away. All of my males are het albino so I always get a nice even 50/50 split of brown and white on all of my litters.