NOTE: This spoiler sent in by GHarris.
The movie opens with young Rebecca looking at beautiful shoes and talking about how there were two kinds of prices: real prices, which bought wonderful things, and her mother’s prices, which bought things that would last forever. We see her receiving a very plain and sturdy pair of brown shoes and looking enviously at the other girls. We see her looking at older girls trying on dresses and jewelry, and not even needing money for these perfect things as they swipe credit cards. She wanted one of those. Now the adult Rebecca (Isla Fisher) is walking down the street, saying little did she dream she would one day have twelve.
Rebecca “Bex” Bloomwood is a writer for a gardening magazine with a closet full of clothes and accessories, and a lot of debt. She does not know the exact amount, but she is concerned to receive one bill for $900. She thinks her card was stolen, but realized that the Outdoor World charge was a going away gift. The debt is all her, and among other things it comes with one persistent collections agent, Derek Smeath.
Heading off to an interview at Alette magazine, run by Alette Naylor (Kristin Scott Thomas), she finds a green scarf in a window that is perfect. Even the mannequin is telling her that it will define who she is. She tries to buy it by spreading the price over cash and multiple cards, but with one card being declined is still $20 short. She rushes to a hot dog vendor, going to the front of the line for an emergency, begging the vendor to give her cash back on a check, even offering to buy all of his hot dogs, claiming she needs the scarf for a sick aunt. The man in the front of the line gives her twenty dollars to get her out of the way so he can get his dog, telling her there is a difference between cost and worth.
With the scarf Bex heads into Alette’s office, but the receptionist tells her that Alicia Billington has filled the job internally. Complimenting the scarf, he tells her that a consumer finance magazine from the same parent company is also hiring, and getting her foot in the door there will help. Bex hurries over to that office, and meets her interviewer, Luke Brandon (Hugh Dancy), the man from the hot dog stand. The interview does not go well, and things get worse as she returns to her job and finds that the magazine is closing, and everyone has received termination notices.
Bex goes back to her roommate, Suze (Krysten Ritter), who tears up her rent check, but it does not resolve the debt problem. With the help of a bottle of tequila they go through the bills, Suze adding figures up, and finding that the news is horrible. However, they get the brilliant idea to write up a sample article for Alette and send it. At the same time, Bex drafts a mean note to Luke.
A call from Luke the next day leads her to realize that she put the letters in the wrong envelopes. He likes her idea of using shoes as a metaphor for investing, but before taking that job, she makes a desperate rush to intercept the insulting letter on its way to Alette. By hiding in a coat rack, stretching, and ending up flat on her back in front of Alicia, she does manage.
Suze also gets Bex to go to a support group for shopaholics, but all she does is send most of the members into a relapse as she describes her love of shopping. Suze also makes Bex watch a video about shopping addiction, and tries to get her to declutter, but Bex really just hides everything in the closet, which later explodes onto and buries Suze.
Bex gets off to a rocky start at the magazine, especially since her card is declined as she tries to buy a finance book. Luke takes her to a company meeting and makes her question the presenter about their bonuses, seeing as the company posted a loss. He asks her to go home and send him a new outline for the article, but a sample sale distracts her. One coat that she buys gives her the answer though, as she sees that it is mostly acrylic and not cashmere, and she writes about changes in credit card terms. Her new column, the Girl in the Green Scarf, is well received. Although the head of advertising is nervous, Bex wins over the company head, bankers, and even Finns from Nokia, as she manages to avoid getting caught in her constant lie that she is fluent in Finnish. At a Miami conference she does well, but is still being harassed by Smeath, whom she has told Luke is an ex-boyfriend that is stalking her.
Still in Miami, she and Luke share a shopping trip and a dance. He reveals that his mother is a wealthy socialite, but he wants to make it on his own. They bond, but she finds out that he is having dinner with Alicia, upsetting her. She also finds out that Alicia will be Luke’s date for an upcoming ball.
Suze convinces Bex not to buy a new dress, but to use something she already has for the ball, but the evening turns out to be jinxed. Her jacket unravels, beads come off and trip an elderly woman, and her dress is similar enough to that worn by the waitresses that she is handed a platter, sending fish onto many of the diners. Luke smoothes things over, and the night takes a turn for the better as he joins her out on the balcony and kisses her.
Bex goes to her parents to ask for help, but it turns out that they have put all of their savings into an RV. They do mention her column, and how much they love it, but she does not reveal that she is the author.
Her work is being so well-received that Bex is given a television spot with Luke, and Alette takes her shopping. While Bex is trying on clothes, Alicia has her bag and takes a call20from Smeath, finding out her debt issues. Bex buys the outfit, though it is a month’s pay, and heads over to her bridesmaid dress fitting, as Suze is getting married. Upset to see the Barney’s bag, Suze sends Bex back to the support group.
Bex meets a new woman going in, and asks her to stash the bags in her trunk. She agrees, but turns out to be the new group leader, Miss Korch, who marches the group to a thrift shop and makes Bex turn over the bags. Bex goes to buy them back after, but only has enough cash for one, so chooses the Barneys dress for the television appearance.
The show is going well, but once things are turned over to the audience for questions, Smeath stands up and exposes her debt issues, as well as the lie of him being an ex-boyfriend. Suze, her fiancée Tarq, and Bex’s parents all see.
As Bex goes back to the apartment, Suze is there, and while they are talking a homeless woman goes by wearing the bridesmaid dress. Suze is furious and moves out. Bex’s parents drive up and offer to sell the RV, but she won’t let them. Alette stops by, and makes an offer to Bex to work at Alette, but since it would involve writing about affordable fashion that is not really affordable, but is encouraging more credit card use, Bex turns her down. Before this happens, Alicia complains to Luke about being stuck with Bex.
Bex returns to her support group, asking for help, and sets up a sample sale and auction of her entire wardrobe. Sending a notice to the original receptionist at Alette, he forwards it to all assistants, including Luke’s assistant Hayley. He says that she will need to make room for all the free samples from Alette.
Everything sells, with the last item on the block being the original green scarf. Two women, including one on a phone, have a small bidding war, but eventually Bex releases it to the winner, telling her not to wear it with yellow and that it will bring her love. In the audience, Hayley has ended up sitting next to Mrs. Bloomwood, who reveals that Bex turned down the Alette offer.
Defending Bex, Luke’s job is in danger, but the owner surprises him by offering to start a new magazine. As they talk, Luke realizes he wants to strike out on his own, possibly inspired by Bex earlier telling him that she could see him running hi s own business.
The grand total from the auction is over sixteen thousand dollars, allowing Bex to pay off her debt. She takes the nine thousand or so odd to Smeath’s office in pennies, giving him what he deserves in the most annoying and inconvenient fashion, as he did to her.
Bex shows up at Suze’s wedding, wearing the dress, which she has traded to the homeless woman for other clothes. They reconcile, and Suze and Tarq are married.
As the newlyweds drive off, Bex wanders down the street. The mannequins call to her again, but as she resists they start applauding her. Exhilarated by her growth, she finds Luke in front of her. He presents her with the green scarf, having sent both of the bidders. They kiss on the street, as she talks about how giving up the shopping has allowed her time for other things, including a relationship with Luke.