Nethergate

Another excellent tale from Norah Lofts about the the old Suffolk country house of Nethergate. At first it provided a welcome refuge for young Isabella de Savigny, fleeing from the terror of revolutionary France. But she was treated with subtle cruelty by Lady Rosaleen Franklin and despised by Martha Pratt, the lady's maid, then she is seduced by the son of the house. She is forced to take drastic and degrading measures to keep herself alive.

I would suggest that you read 'Jassy' before starting 'Nethergate' as this book seems to be the sequel.