Final answer:
Aunt Virginia's self-possession suggests her acceptance of mortality, reflected in her composed and dignified demeanor which aligns with themes of peace with life's cycle, as indicated in the poem.
Step-by-step explanation:
In the context of the poem, Aunt Virginia's self-possession or 'intactness' most likely clarifies her serene acceptance of mortality. The description of Virginias as being at ease with her surroundings, much like the Roman and Etruscan matrons unaffected by time or decay, combined with the references to her 'imperial finery', suggests a person who is dignified and at peace with the cycle of life. Furthermore, the notion of being veiled, as with whiteness related more to death than purity or the use of veils in Wheatley's poetry to communicate a subtlety, may also indicate a kind of acceptance or peace rather than fear, defiance, or detachment.