The death of Mrs. Wayne, and her subsequent burial, are significant as they show the degree to which Chance has become disconnected from his past, a past he so desperately tries—but fails— to regain. Chance's mother passed away during his lengthy absence from St. Cloud. Her doctor sent Chance numerous letters informing him of his mother's condition, but he never received them. Mrs. Wayne mustn't have had much money because a church collection was required to pay for her funeral expenses.
Mrs. Wayne's death and burial could be seen as symbolic; with her passing, a vital link between Chance and his charmed youth has been broken forever. One of the reasons that Chance returned to St. Cloud was to see his mother after all these years. But just as he'll never see his mother again, so he'll never get a chance to recover the youth to which the memory of his mother is so inextricably linked.