Wife for a Day by Patti Berg

Millionaire rancher Jack Remington hadn't expected trouble when he flew to Palm Beach for his sister's engagement ball. But his girlfriend called it quits and now his sister is anxious to meet the woman who's captured his heart. Then, a beguiling, flame-haired enchantress breezes into his hotel room with a tux and a seductive smile, and Jack's sure his troubles have come to an end. All he has to do is hire the beautiful tailor to be his fiancee—for just one night.

Samantha Jones is sure the sexy cowboy is out of his ever—lovin' mind. She's never been to a ball, never worn a fancy gown, and has no idea how to act like a socialite. She can't possibly pose as his wife-to-be. But trouble's been following Sam for too many months and the money Jack's offering is something she can't refuse. There's only one problem—their pretend kisses make her feel something very real—and there's the possibility that just one night will never be enough.