My niece wants to marry a Frenchman, what should I do?

I come from Italy, but moved to France when I was a young man. Since then, France became my native land, and I even changed my name a little (dropped the last -i) to make it sound more French. In France, at first I worked for a very important government man, Armand-Jean Plessis, when he died, I got employed by a very powerful widowed French woman (can't tell you her name, of course). She was very nice to me, and treated me like a family, not only like her adviser. My employer had a son, Louis, an extremely gifted and handsome young man. I had no children, but brought from Italy my nephews and nieces, to help them in their life and careers. They all did well here. My employer allowed my nieces to meet her son freely (at public places, parties and such, of course), and they all grew up together like a family. Now her son Louis is set to be married to a well off Spanish girl, Maria Theresa. But, one of my nieces, Maria, spoiled it all. She simply threw herself on young Louis. They ride horses together (she is an excellent equestrian, and so is he), gossip together and go out together. Louis is madly in love with Maria now, and my employer is not happy about it! And all we achieved in this life happened through her. She is very cool to me recently, and there is a rumour that Louis want to marry Maria, who is a penniless girl, and not a great beauty! It means my career is over! What should I do?