The answer is yes, they were digging on her grave. In the poem itself, it really was her dog descrating the grave, just burying a bone. There's something kind of charming about a dog digging up its old master and playing fetch with the corpse's femur.
Lit Brick is a comic started by Jodie Troutman in an effort to read the entire Norton Anthology of English Literature. Having eventually succeeded in that goal, it now features comics about all manner of random literature. For more of Jodie's work, visit troutcave.net!