I think that what catnapper above said is exactly what is going on. Our Lizzie does this and I have learned to pet her cautiously and can usually see signs that she is overstimulated - like contorting her body, looking up at me, moving her head around... as if she loves the rubbing but is about to bite. Maybe your grandma can think of it as a "lovebite" because it is likely not Sasha really biting her (like an aggressive bite)