The title tells us that this poem is a portrait of a woman, so we should have a pretty good sense of who this woman by the end, right? Um...not really. "Portrait d'une Femme" ends with the line, "Yet this is you" (30), but we're not really clear what "this" means. The speaker doesn't describe the woman so that we can say, "OK, her name is Liza, she grew up in California, she's a bit shy but very funny, and she likes the color blue." Instead, we get a mishmash of the speaker describing what are probably her social interactions and possessions alongside various objects floating around on the sea. In fact, we even have a hard time distinguishing between straightforward description and pure metaphor. Clearly a conventional sense of identity doesn't work here; the poem shows us a very different process in determining and characterizing a person.
The speaker's empathy with the "femme" makes clear that the speaker is also a woman.
We can read the poem as a long list of images and experiences that belong somehow to the woman (her "great store" of "riches"), and yet the poem concludes by saying that nothing is quite her own. This suggests that the woman's most defining characteristic is her dissatisfaction – she constantly feels that she is lacking something.