Dido's role in the Aeneid

There seem to be two basic arguments as to why Vergil focused so much on what could have been just an insignificant episode in the course of the founding of Rome.  The most compelling is that Dido serves as a counter point against Aeneas' pietas (not piety in an religious sense but rather loyalty or devotion, especially towards one's country).  Dido and Aeneas meet each other as equals; both have been exiled, are destined to establish a new city, lost their mates, and are dux.  An important detail that is easy to miss is Dido's devotion to her deceased husband and her refusal to even consider any suitors.  This is classic Roman pietas.  Her mental state, however, immediately begins to fall apart in Book IV.  The first line begins with At regina iamdudum (But the queen already) so before we even read the verb it is abundantly clear that it has already happened.  This is also in sharp contrast to the last word of Book III Aeneas . . . quievit (Aeneas was calm/quiet).  There are a series of similes describing Dido and Aeneas.  The first portrays Dido as a deer wounded in the woods, then Aeneas is equated to the god Apollo, then Dido is compared to a Baccant, Aeneas to an oak, and finally Dido as madmen pursued by the furies.  As she is consumed by love she neglects her duties as a leader; the city walls are no longer being built (walls are an important image for power in the Aeneid).  Dido's passions are in stark contrast to Aeneas' steadfastness.  The Romans were overwhelming Stoic - they praised the moderation of emotion - and Dido's unrelenting laments, especially coming a person of duty, would be highly suspect.  Aeneas' duty is to found Rome (some would even say that Rome is the true protagonist) and how can he disregard Jupiter's orders to leave Carthage or ignore his father's ghost telling him that he is denying his offspring of their inheritance.  Romans placed the highest emphasis on the Mos Maiorum - the custom of the ancestors; the duty of the pater familias.  Dido eventually calls herself impia and realizes how far she has fallen and her suicide redeems her pietas, or does it?  Does she kill herself out of love or out of impia?  When Aeneas later sees Dido in the underworld she ignores him and walks away with her first husband, her true love, the one she was devoted to.  Thus Vergil did redeem her.