I hope you can find a mentor close. It is not as easy as some think. How far along is she? I don't give mine anything but good quality kibble. I add some wet food in the last couple weeks but not to much. No calcium before she whelp is very important. After she needs extra calcium
Here is some good information to start.
Dog Breeding and Canine Reproduction by Debbie Jensen. Dog Breeding and Whelping guide for dog breeders.