I'm not a good guesser at these things, but she looks to be carrying more than 3. Also, I've never had my girls have such pronounced nipples with a first pregnancy. I mean, they do get bigger with pregnancy but those look like they've been suckled before.
For her to even think of reducing her food makes me wonder just how capable this lady is...maybe she's just been lucky up to now.
Have you shared any info from the Debbie Jensen site with her? Here's the link again.
Dog Breeding and Canine Reproduction by Debbie Jensen. Dog Breeding and Whelping guide for dog breeders.