Charlotte "Charlie" Cantilini (JENNIFER LOPEZ) is an attractive and hard working woman who holds down so many different temp jobs that she doesn't have time to date anyone, much to the concern of her best friends Morgan (ANNIE PARISSE) and Remy (ADAM SCOTT). Things change, however, when she repeatedly runs into handsome doctor Kevin Fields (MICHAEL VARTAN) whose ex-flame, Fiona (MONET MAZUR), is still so attracted to him that she tells Charlie that he's gay.
Of course, he's not and asks Charlie out, with the two quickly falling in love. Like any good son, he wants his girlfriend to meet his single mom, Viola (JANE FONDA), a former TV talk show host who had a breakdown after losing her job to a much younger and prettier, but dim woman. Seemingly recovered, Viola -- along with her personal assistant Ruby (WANDA SYKES) -- can't believe her ears when Kevin proposes to Charlie in front of her.
Viola tries to look calm, but immediately sets out to nip the pending marriage in the bud, any way she can, including moving in with Charlie after feigning another pending mental breakdown. Charlie tries to grin and bear it, worrying that her future mother-in-law is really an unstable and troublesome person. Yet, when she discovers Viola's real motives, Charlie plans to get even, thus leading to a battle of wills, wits and various forms of subterfuge.