The narrator of "Some Women" in Munro's collection of short stories, Too Much Happiness, is an older woman telling her reminiscence of a summer job she held in 1940 when she was age 13. This vulnerable age sees much but also fails to understand much that is seen, as experience is still veiled by innocence (at least in earlier eras it was).
Her employer is Mrs. Crozier whose son--who lives upstairs with his educated wife, Sylvia--is dying of leukemia. Understandably, at this point in his life, physical passion is not a preeminent part of his experience. Mrs. Crozier doesn't like Sylvia and blames her--along with the rest of the town--for teaching summer school instead of staying home with her dying husband.
Enter Roxanne, a rather sexy and vain woman hired to give Mrs. Crozier massages. A wicked plan hatches between the two of them to turn Mr. Crozier's affections against Sylvia through an attempt at renewing the dying man's physical passions via Roxanne’s ministrations.
It is in this context that the narrator says of her younger self that:
The carnality at death's door--or the true love, for that matter--were things I had to shake off like shivers down my spine.
Here, she is expressing her surprise and shock ("shivers down my spine") at observing how base and carnal (i.e., physical) selfish individuals, like Roxanne, could be when standing in the face of death: Impending death should be the one overriding consideration, yet physical pleasure could demand that death be forgotten. The narrator observed the same about the forces of true love, like Sylvia's, in the face of death with the same surprise and shock. In other words, to the narrator's 13-year-old mind, nothing selfish-seeming should come before a person's impending death in importance.
Thank you very much for your enlightening explanation. I will reread the story with your synopsis in my mind.