Is her corpse rotting?
Yes.
From the moment we die in this temporal world, our bodies begin to rot. Definition of rot: "To undergo decomposition, especially organic decomposition; synonym: decay"
Now here's the truth of the matter: "In the sweat of thy face shalt thou eat bread till thou return unto the ground, for out of it wast thou taken; for dust thou art, and unto dust shalt thou return.” - Genesis 3:19
Connecting the dots >>> in order for our dead bodies to go from flesh to dust, our mortal flesh must rot away - what remains is dust.
Most important: There is no veneration of corpses or their dead body parts in scripture. The nun who lived on earth is not here. She has a new immortal body in heaven.