The Proposal

Margaret Tate is an executive editor in chief of a book publishing company. After learning she is about to be deported to Canada because she violated the terms of her work visa, she persuades her assistant, Andrew Paxton, to marry her. She reminds Andrew that if she's deported, the work he put in as her assistant will be lost, and he'll be set back in his dream to become an editor. Mr. Gilbertson, a U.S. immigration agent, informs them that he suspects they are committing fraud to avoid Margaret's deportation. Gilbertson tells them that they'll be asked questions about each other separately. If their answers don't match, Margaret will be deported to Canada permanently and Andrew will be convicted of a felony punishable by a $250,000 fine and five years in prison. Andrew insists that Margaret make him an editor after their marriage and publish the book he's been recommending to her. Margaret agrees.
The couple travels to Sitka, Alaska, Andrew's hometown, to meet his family. Margaret meets Andrew's mother Grace and grandmother Annie a.k.a. "Gammy". During the trip to the family home, Margaret notices that nearly every shop in town carries the name Paxton and learns that Andrew's family is in fact very wealthy. During a welcome home party, Andrew confronts his father, Joe, who is angry about Andrew's dating the boss he has so long disliked and thinks he is using her to get ahead in his career. After their argument, Andrew announces the engagement to everyone. Margaret also meets Gertrude, Andrew's ex-girlfriend.
The next day, Grace and Annie take Margaret to a local bar to watch a strip dance by a locally famous but over-the-hill exotic dancer, Ramone. Stepping away from the show, Margaret learns from Gertrude that Andrew wanted to become an editor and make his own life and that Andrew had proposed to Gertrude. However, Gertrude refused because she didn't want to leave Sitka for New York. Returning home, Margaret learns of the conflict between Andrew and Joe. That night, Margaret asks Andrew about his relationship with his father, but Andrew refuses to talk. Instead, Margaret opens up to Andrew.
The next day, the family convinces them to marry while they're in Sitka. After Margaret realizes how close Andrew's family is, she becomes upset, gets on Andrew's boat, and speeds away with him. She tells him she has been alone since she was sixteen years old after her parents died and had forgotten what it felt like to have a family. She lets go of the helm and stumbles to the back of the boat. Andrew makes a sharp turn to avoid hitting a buoy, and Margaret falls out of the boat. Andrew quickly turns the boat around and saves her because she can't swim. At the wedding ceremony, Margaret confesses the truth about the wedding to the guests, including Gilbertson, who informs her she has twenty-four hours to leave for Canada. Margaret returns to the Paxton home to pack her things. Andrew rushes to their room only to find Margaret has already left, leaving the aforementioned book manuscript with a note of praise and a promise to publish it. Gertrude attempts to comfort Andrew and asks if he is going to go after her. As he rushes out to find Margaret, another argument arises between him and Joe. Annie fakes a heart attack and convinces them to reconcile before she "passes away". After she succeeds in getting things moving again, she owns up to faking the heart attack. Andrew's parents realize he really loves Margaret. He goes to New York and tells Margaret he loves her in front of the entire office staff. They kiss, then go to Gilbertson and inform him they are again engaged, but for real this time. The film ends with Gilbertson asking questions (some of them irrelevant) not only to Andrew and Margaret, but also Joe, Grace, Annie and Ramone.

Question: Why does Margaret become upset?
Answer: she realizes how close Andrew's family is