What is the analysis of the character of the Duchess in "My Last Duchess"?
In spite of the Duke's rather untrustworthy opinion of the Duchess, we can infer a number of physical and other attributes from what he says about her. It is pertinent that she was beautiful and that he wanted to celebrate her allure by having her portrait done by a renowned artist.
When he discusses the painting, he mentions her blushing ('spot of joy') not only because he was there but also because of a remark the painter, Fra Pandolf, made while executing his task. This suggests that she was somewhat shy and probably easily embarrassed by a compliment or by seeing her husband perusing her and the painting being crafted by the artist. The Duke, however, seems offended since he believes she was too easily pleased.
A heart—how shall I say?—too soon made glad,
Too easily impressed....
...she liked whate’er
She looked on, and her looks went everywhere.
Sir, ’twas all one!
...all and each
Would draw from her alike the approving speech,
Or blush, at least.
...She thanked men—good! but thanked
This grew; I gave commands;
Then all smiles stopped together. There she stands
As if alive.
The Duke, who narrates the poem, is an unreliable narrator. Thus in trying to determine the character of the Duchess, we have the problem that we cannot trust our only source of information.
The basic facts of which we can be certain are that she was married to the Duke, that she was young and probably beautiful, that she died, and that the Duke is negotiating for a second wife. We can also assume that she was a member of the nobility.
The Duke portrays her as flirtatious and disloyal. He objects to the way she "thanked men" and suggests that rather than favoring him, her husband, she treated him just like any other man rather than loving or respecting him as a husband.
As readers, though, we cannot trust the Duke, who appears insanely jealous and paranoid and may well have had her murdered. She may well have been simply polite and pleasant. Eventually, we cannot determine her real character because we are not given an account by a reliable witness.