I even had a mother start killing her babies in front of me. She only had 5 left and when i moved one of the babies, she just started goreing them and i couldn't believe it, i was able to save 3 babies by giving them to another mother. Mice on their first litters aren't good at all, in fact it is straight up wrong!

Don't fret it, she will get over it and have many many babies in the future. At least they aren't as bad of mothers as guinea pigs are...