Damaris Myddleton

Damaris Myddleton

Plays and sings beautifully.

Has a ruby and an emerald necklace.
Lived in Birch House, Worksop.
Came under the guardianship of Lord Henry Malloren, Rothgar's uncle.
  Lord Henry's home is Thornfield House.
Then into guardianship of Rothgar, 3rd Marquess of Rothgar.

Father: Marcus Myddleton, merchant adventurer/pirate.
Mother:

Has half-brother Mark, who goes by Butler-Myddleton. Sometimes called Mark Myddleton,
  son of Rosemary Butler, b Oxted, sometimes called Rose Myddleton.

Married: Octavius Fitzroger from Winter Fire and A Most Unsuitable Man.

Her lawyer: Mr Dinwiddie.
Maid: Maisie Duncott.

I think this Gainsborough portrait from the right period looks a little like Damaris [bottom-left pic].
"A little tall, slim, straight-backed, apparently confident.
Brown hair, commonplace features, bright eyes, wide smile. Long lidded eyes, cat like."

Heroine of A Most Unsuitable Man.