The word "rococo" derives from "rocaille" meaning "shell work" which was a favourite ornamental device of the period.I love everything about this picture. The light, the shimmering gown she is wearing, her writing desk, her little companion and the way she looks back as if daring us to confront the contents of her little gift. Maybe she's the one hiding the note!
Rococo was a reaction against the grand style and subject matter of the Baroque period. The style was characterized by pastel colours, graceful curving forms and a light-hearted mood. The subject matter was often a dramatic aristocratic love scene in a decorative natural setting.
What do you suppose is in the note? I think she is blushing at our intrusion and that little dog looks guilty enough.