It could well just be because its her first litter it may also be due to lack of protean. To overcome this some people offer cat biscuits as part of their feed.
Also are you sure it was the mother that killed the babies. Some times you will get a female in a group that never seems to produce and just goes around eating everyone elses babies.
Your best place to look on here is the feeder section. If you go back through the posts there's loads of info in that section that will help you.