One...

Be his mistress.
What could be so hard?
Rosy born from nobility. Her life set until things took the wrong turn and now she finds herself a mistress of a man who has placed her in the estate his wife and child reside in.
She had placed her life of nobility in the past but she can't run from it if she is his mistress.
And leaving him would be her best option only she doesn't know the obsession he has over her.
The level he will take to keep her with him.