Final answer:
The additional fact associated with Van Dyck's 'Mrs. Kirke (Anne Killigrew)' is that Fido the dog in the portrait symbolizes the girl's loyalty, following the convention of using dogs as symbols of fidelity in portraiture.
Step-by-step explanation:
The painting by Van Dyck titled 'Mrs. Kirke (Anne Killigrew)' is most closely associated with the additional fact that Fido the dog shows his loyalty to the girl in the portrait, option (a). This aligns with the historical conventions in portraiture of the era, where dogs were often included as symbols of fidelity, especially in female portraiture to demonstrate qualities of the subject, such as loyalty or faithfulness in marriage.
As can be seen in other works from the Renaissance period, like 'The Arnolfini Portrait' by Jan van Eyck or pieces by Vermeer, domestic animals like dogs would symbolize traits or convey certain messages about the sitters. Hence, portraying a dog in the painting was more than a simple inclusion of a pet; it played a role in communicating personal virtues.