I can not remember what the title of the movie is. It is about a girl who lives with her relatives and is treated as a servant. Only the father treats her well. Later on they discover that she is actually a noble lady (she is his daughter). There are other girls in the family. It is something like Cinderella story. The main protagonist (the girl) loves horse riding. She even takes part in a horse competition although she is a woman and women are not allowed to compete. She meets a handsome gentleman. All the other girls are in love with him.
I thought Durmont Mulroney was this gentleman but I might be wrong.
The film is similar to Mansfield Park, Northanger Abbey and all these movies based on Jane Austin books. I think the movie is American, not British.

I'm pretty sure it's The Inheritance (1997) (TV) (http://www.imdb.com/title/tt0119369/)