I Am The King's Mistress.

This is about a girl that was born in Scotland then uprooted to France with her family to find a new life for herself. She runs into an old friend when he parents drag her along to French Court. Her parents were French and decided she should also live a life in the troubling times that were occurring in France. She falls hard for the one she's introduced to as Lady Margaret. The one she knows she can't have. King Francis. He visits her in the garden one night as she takes a leisurely walk and offers her the chance to be the one thing ANY woman in France would love to be. His mistress.