Anne Justine Angèle Delva de Dalmarie, who is thought to be the eponymous Black Countess in the painting by Henri de Toulouse-Lautrec. Where would I go to find out more about her?
Five months is better than nothing I guess? Found this while google searching for the countess. I highly recommend tracking down the article which announced the discovery and outlines everything known (which is sadly little) about her:
Oliver Wunsch, "Henri de Toulouse-Lautrec's 'Black countess' Identified", The Burlington Magazine (October 2019), Vol. 161, No. 1399, pp. 840-845