High School Musical 2

The school year ends with everyone at East High School looking forward to summer vacation ("What Time Is It"). Troy Bolton is still dating Gabriella Montez, who decides to stay in Albuquerque with her mother. Troy eventually decides to look for a summer job to gain money for college.
Sharpay and Ryan Evans plan to spend part of the summer at their family's country club, Lava Springs ("Fabulous"), but Sharpay's summer plans also include pursuing Troy, whom she has arranged to be hired at the club. However, Troy convinces the club's manager, Mr. Fulton, into hiring Gabriella and their close group of friends as well; including Taylor and Chad. Sharpay is enraged upon learning that Gabriella is working as one of the lifeguards, but is unable to get her fired. So she orders Fulton to give them difficult tasks so they would be best to quit. Fulton attempts to intimidate the group, but Troy rebuilds their confidence and convinces them that they can persevere ("Work This Out").
Troy continues to worry about funding for college. Sharpay senses his need and arranges for Troy to be promoted, hoping that this will convince him to sing with her at the talent show. Meanwhile, Kelsi writes a ballad for Troy and Gabriella. Troy agrees to sing with his friends in the show ("You Are The Music In Me"), not knowing that Sharpay is vying for his attention. (In the extended version, Sharpay and Ryan trap Troy as he prepares for a date with Gabriella, and perform their potential show stopper ("Humuhumunukunukuapua'a").)
Ryan realizes he does not mean much to Sharpay anymore, as she is ready to blow her brother aside for the opportunity to perform with Troy. This leads to tension between the twin siblings and Ryan angrily informs Sharpay that he will no longer obey her orders. Taylor and Gabriella invite Ryan to the baseball game, where he persuades the Wildcats to take part in the talent show ("I Don't Dance").
Troy and Gabriella's relationship is strained when Troy sees Ryan with Gabriella, sparking jealousy. Owing to a "promise" from Troy, he and Sharpay practice their song for the Midsummer Night's Talent Show ("You Are The Music In Me (Sharpay Version)").
When Sharpay discovers that Ryan and the Wildcats are putting together their own performance in the show, she orders Mr. Fulton to ban all junior staff members from performing. Gabriella angrily confronts Sharpay about her interference and quits her job at Lava Springs. Troy overhears the exchange, and tries to persuade Gabriella to change her mind. Gabriella expresses her loss of trust with Troy ("Gotta Go My Own Way") and leaves Lava Springs, and gives him the necklace back. It also seems that they broke up.
Troy returns to work the next day to find that his friends refuse to talk to him. Kelsi silently shows Troy the notice from Mr. Fulton, causing Troy to question his own motivations ("Bet On It"). He begins to reconcile with Chad and his other friends. Then Troy confronts Sharpay, informing her that he will not sing with her. The Wildcats and Chad forgive Troy for his absence and convince him to sing in the talent show, which he does only under the condition that they are all allowed to perform as well.
At Sharpay's supposed instruction, Ryan gives Troy a new song to learn moments before the show. As Troy goes onstage, he asks Sharpay why she switched the song, and Sharpay is shocked to find that her brother tricked her. Troy sings the song ("Everyday") alone, until Gabriella surprisingly joins him onstage. In the end, Sharpay proudly presents her brother, Ryan, with the award for the talent show. After the talent show, all the Wildcats go to the golf course to enjoy the fireworks.
Everyone celebrates the end of the summer with a pool party ("All for One") which features a cameo appearance by Miley Cyrus.

Question: Why is Sharpay enraged?
Answer: she learns that Gabriella is working as one of the lifeguards.