Lost Lady by Jude Deveraux

When 17-year-old Regan Weston discovers that her upcoming marriage is merely a financial scheme devised by her uncle, she runs mindlessly through the dark streets of London, feeling homeless and unloved. There a ruggedly handsome, domineering American, Travis Stanford, spots her nightgown-clad figure and, assuming the worst, takes her to his bed for his pleasure.

The next morning Regan refuses to tell him where she came from, and Travis informs her that her future is in America with him. Who is this sometimes gentle, sometimes overbearing man? Horrified of living with him in a savage new country, Regan is humiliated to feel herself falling in love with him by the time they dock and mortified when he abruptly marries her without even proposing!

Struggling to manage his massive Virginia estate, pregnant with his child, Regan feels she cannot compete with the confident, flirtatious Margo Jenkins, a woman who will do anything to win Travis. For how can Regan dare to claim the love of a man she fears she may have in name only?