Housesitter
(1992)

Gwen (Goldie Hawn)'s plan works, so Newton (Steve Martin) reconciles with his parents and gets the promotion he wants. When Becky (Dana Delany) shows interest in getting back together with Newton, Gwen reveals that she wanted their "marriage" to work, and leaves him. Newton chases after her and confesses how much he needs her. Gwen stays, and the pair live happily ever after. Just before the end credits, Gwen confesses that her real name is Jessica.

Thanks Annie!