"Diaphanous Portrait Of An Elegant Woman"
Sometimes we add to the descriptions: portrait of a lady of quality… This would imply that the person could afford or be offered her portrait painted on an ivory plaque by a specialized artist… Sure that at the time, not very wealthy, you could stay and go anonymous. The delicate gilded wooden frame seems original to me. The use of ivory as a support for the execution of miniatures was in vogue in the 18th century and at the beginning of the 19th, until the invention of photography. Provenance of a noble family but the young lady is not named. Signature of the artist clearly legible. 
Le Magazine de PROANTIC
TRÉSORS Magazine
Rivista Artiquariato