What's the Name of That Book??? discussion

A young woman meets a young man who takes her to France along with her aunt - he buys her clothes and dazzles her. They may even get married. He takes her to a law office where she signs some paperwork. Later in the book she is introduced as a woman to someone named I think Magnus - he believes she is the missing heiress he was in love with. Everyone tries to convince her she is the other girl. Later they find out she is the twin of a missing woman and the first man used her to get her twins inheritance

Any idea what year this was published? If not, when did you read it and was it old or new then?

Sent PM and link, but OP has no activity in three years - next mod. can move to abandoned.