Fortune's Mistress

"Their marriage seemed very modern, open
Maggie, the freewheeling socialite, dispensing her favors indiscriminately--and Finn, running the family businesses and indulging his playboy tendencies. Then Finn fell genuinely in love--with Laurie Fortune, young daughter of financier Nicholas Fortune-and the house of cards Maggie's scheming had created fell about her ears.
Because Nick thought Laurie wanted to be friends with Maggie and he was set on wresting her away from this ""scarlet woman."" And Maggie was horrified to realize that her unexpected response to Nick was returned in full measure."