The old woman

Just as a Cacambo is the faithful, resourceful servant of Candide, the old woman is the faithful resourceful servant of Cunégonde.
We first meet her, when, on Cunégonde’s instructions, she shelters Candide and looks after him, after his flogging at the Auto-da-fé.  When he is recovered, the old woman then takes Candide to a sumptuous house where Cunégonde lives, sharing the attentions of two men.

The old woman is unsentimental.
When Candide and Cunégonde are reunited an emotional scene follows.  When Candide and Cunégonde swoon with ecstasy of the old woman smothers them in the smelling salts.  As they, chatter, sigh, weep and shout, she tells them to make less noise.

The old woman is practical and decisive
After Candide has killed in quick succession Don Issachar and the Grand Inquisitor, the lovers are at a loss to what they can do.  It is the old woman who advises escape to Cadiz taking Cunégonde’s money and jewels with them.

When on the route to Cadiz man they are robbed are, the old woman alert enough to identify the culprit.  It is a reverend Franciscan friar who had slept at the same inn.  Again it is the old woman who suggests how they can find some other money for their journey, with the idea that they could sell one horse.

The old woman puts expediency before principle.
When they arrive in Buenos Aires, the governor, who is a great womaniser, is attracted to Cunégonde and offers her marriage. She asks a quarter of an hour to make her mind up and consulted the old woman. She says that as Cunégonde hasn’t got a penny and has suffered enough already, she should marry the governor and goes on to give reasons - comically incongruous and not morally admirable.  She tells Cunégonde that he is the grandest lord in South America and has a fine moustache. 
…. il ne tient qu'à vous d'être la femme du plus grand seigneur de l'Amérique méridionale, qui a une très belle moustache;

When the old woman hears that the magistrate’s officials from Portugal have arrived on their trail, it is she who advises the two what to do.  Chapter 13 Page 87:
….le gouverneur, qui vous aime, ne souffrira pas qu'on vous maltraite; demeurez.» Elle court sur-le-champ à Candide: «Fuyez, dit-elle, ou dans une heure vous allez être brûlé.
That Candide is losing his true love does not trouble her unduly.

Her resilience in the depths of her despair
As with Martin, the old woman has been made a pessimist by her experiences in life.  Chapter 12 Page 84
 - je voulus cent fois me tuer, mais j'aimais encore la vie. Cette faiblesse ridicule est peut-être un de nos penchants les plus funestes; car y a-t-il rien de plus sot que de vouloir porter continuellement un fardeau qu'on veut toujours jeter par terre? d'avoir son être en horreur, et de tenir à son être? Enfin de caresser le serpent qui nous dévore, jusqu'à ce qu'il nous ait mange le cœur?

The old woman cannot stand the boredom of inactivity
In spite of all the sufferings of her life, the old woman finds their peaceful existence in Turkey, where they finally retire, utterly unbearable and she expresses her views very strongly and presents the final question of the book to Candide. Chapter 30 page 147

«  Je voudrais savoir lequel est le pire, ou d'être violée cent fois par des pirates nègres, d'avoir une fesse coupée, de passer par les baguettes chez les Bulgares, d'être fouetté et pendu dans un auto-da-fé, d'être disséqué, de ramer en galère, d'éprouver enfin toutes les misères par lesquelles nous avons tous passé, ou bien de rester ici à ne rien faire?  
« C'est une grande question, dit Candide.

How advanced old age changes her.
In the final chapter we are told that after she had settled in Constantinople with Candide, she began to show the effects of her advancing years, becoming infirm and ill tempered.  However when Candide develops his new code of living based on the satisfaction of hard work, she, the daughter of a pope, plays her part by doing the laundry. 

The old woman’s role in this conte philosophique

By means of the story of the old woman, Voltaire is able to add to his list of the evil and disastrous events of his century

The life story of the old woman demonstrates the absurdity of the philosophy of Optimism
The old woman’s life story is told in a digression in chapters in 11 and 12.  By including this, Voltaire is parodying the traditional picaresque, where such digressions inform us of the previous adventures of new episodic characters.  The old woman is provoked to tell how life story to disprove Cunégonde’s claim that the old woman could not have suffered a worse fate than hers. 

The humour which the old woman introduces
There is the general humorous irony of the whole of her biography because each incident so neatly caps and so clearly surpasses that of Cunégonde
Humour arises from a matter of fact acceptance of these horrors of life.  She tells us for example that her lover took two hours to die in dreadful pain:
Page 79 - une vieille marquise oui avait été maîtresse de mon prince l'invita à prendre du chocolat chez elle. Il mourut en moins de deux heures avec des convulsions épouvantables. Mais ce n'est qu'une bagatelle.

The old woman apologises for telling all her life story on the voyage but excuses herself by saying it is the normal practice to kill time in this way.  – Most would agree that the recounting of such sensational experiences has a far more obvious justification.