Mother Livestock Guardian Dog lovingly nibbles her 4 year old daughter

Maple loves her puppies forever. She is now 10 years old and has had 2 litters of puppies; and 4 year old Wynter is one of her daughters that we kept as a working sheep guardian along with her brother Greyson. Mother dogs often do this love nibbling/grooming behavior with their young puppies, but Maple continues to do it into her puppies' adulthood. Wynter has no complaints and will often lie down in front of Maple and roll onto her back to get attention like this.