Mallrats

The day prior to the events of Clerks, college student T.S. Quint (Jeremy London) is preparing for a trip to Universal Studios in Florida with Brandi Svenning (Claire Forlani), during which he plans to propose to her; however, Brandi tells him she cannot go because she has volunteered to fill in as a contestant on Truth or Date, her father's dating game show. They argue over this and eventually break up. T.S. turns to his best friend Brodie Bruce (Jason Lee), who has also broken up with his girlfriend, Rene Mosier (Shannen Doherty), after having an argument, and Brodie suggests the two might find comfort at the local mall.
Brodie and T.S. discover Truth or Date is being filmed at the same mall, through their friend Willam (Ethan Suplee, who throughout the movie tries to see a sailboat in a Magic Eye poster), and ask local drug dealers Jay and Silent Bob (Jason Mewes and Kevin Smith, respectively) to destroy the show's stage, a task for which they devise elaborate but ultimately unsuccessful plans. These actions result in the two being pursued by mall security guard LaFours (Sven-Ole Thorsen), but they are able to escape him. Brodie finds out Rene began a relationship with his enemy Shannon Hamilton (Ben Affleck), a clothing store manager who hates Brodie because of his "lack of a shopping agenda." Brodie confronts Rene to find out more about her relationship with Shannon, and the two have sex in an elevator. Brodie is later abducted and attacked by Shannon, who intends to have sex with Rene in a "very uncomfortable place", a reference to anal sex. (As a running joke, this is interpreted as the "back of a Volkswagen".) As a result of this incident, Jay and Silent Bob assault the mall's Easter Bunny, under the incorrect assumption that he attacked Brodie.
Brandi's father, Jared (Michael Rooker), who is aware of Brodie and T.S's presence at the mall, has the two arrested on false charges of drug possession. Jay and Silent Bob are able to rescue Brodie and T.S. and are once again able to evade LaFours. Meanwhile, Brodie and T.S. seek refuge at a local flea market, where they meet fortune teller Ivannah (Priscilla Barnes). T.S. decides to win Brandi back and the two return to the mall.
Before the show begins, Brodie receives advice on romance from Stan Lee, who was visiting the mall. After this, Brodie requests that his friend Tricia Jones retrieve footage of her having sex with Shannon. Tricia herself was doing a project in which she had sex with a number of male adults, despite being only 15 years old, for a book about the sex drive of men. Meanwhile, T.S. also persuades Jay to get two of the game show contestants stoned, which allow him and Brodie to replace them on Truth or Date. The initial plan was all three contestants but the third one, Gil Hicks, showed up late, and Brodie and T.S. must go on with him.
During the show (which Brodie continuously heckles by telling bizarre stories), Brandi recognizes the voices of Brodie and T.S., and an on-air argument between the three ensues. Brodie tells Brandi that T.S. had spent all day trying to win her back. T.S. then proposes to Brandi, which she accepts. As the police arrive to arrest T.S. and Brodie after the show is over, Silent Bob plays a sex tape of Shannon and Tricia, resulting in his arrest for statutory rape. Brodie and Rene renew their relationship as a result.
The conclusion reveals that T.S. marries Brandi, Tricia's book is a bestseller, Shannon is imprisoned (and subsequently anally raped), Willam eventually does see the sailboat, and Brodie becomes the host of The Tonight Show (with Rene as his bandleader) after impressing the show's producers with his stage banter. Jay and Silent Bob are also shown with a monkey named Suzanne, which promises to be "another story" (told in Jay and Silent Bob Strike Back).

Question: Why did Brandi say she couldn't go?
Answer: Because she has volunteered to fill in as a contestant on Truth or Date