False pregnancy, or pseudocyesis, is a common condition in female intact dogs. Signs include swelling of the mammary glands, lactation, not eating, and "mothering" small objects.
Her novel is particularly astute about the ambiguous feelings elicited by mothering, a theme that has been picked up anew by female writers in the 21st century.
Maternal inheritance gave rise to the idea of a Mitochondrial Eve, a woman who lived between 180,000 to 580,000 years ago from which all human mitochondrial DNA is rooted.
Now if the female was actually defending its young, then the attendant sense changes the equation. and consequently the intensity of battle might be different.