Jennifer Lopez -- My Grudges Are Gone, Girl

Jennifer Lopez is all about her ex-boyfriends this week ... first she hung out with Diddy at a nightclub -- then she checked out her ex-fiance Ben Affleck's hit movie, and offered some strange proof.

Lopez went to see "Gone Girl" Saturday night ... which we know because she posted a pic of her feet up in the theater with the caption, "#GONEGIRL." Weird, but maybe her booty isn't the only thing fans dig.

As we previously reported ... Diddy reunited briefly with J.Lo at Hooray Henry's this week.