I can't remember the title of a book!!!?

I read a book a while back and it was hilarious! It was about a girl in her 20's that was a fortune teller or a psychic or something and she was asked to lie to a client by the clients family. It envolved a tangled web of diaster and humor and somewhere in there, something to do with a diamond ring. I think the cover was pink and had a martini glass and diamond ring on it... any help????