Malina makes her first appearance in the movie as one of the participants at the Turtle Bay Resort Invitational surfing competition. Malina finds herself in first place in the first heat of the competition, with Bethany in second. Malina and Bethany paddle battle for the next solid wave, although Malina gets to it first and carves out a high-scoring ride. In the final heat of the competition, Bethany beats Malina to a huge wave and pulls off the highest-scoring ride of the day, putting Bethany in first place. At the awards ceremony, she invites Alana (who took third place) and Malina (who took second) up onto the winner's podium, but the latter walks away resentfully.
After the Rip Curl company decides to sponsor Bethany and Alana, the two girls stormed off to go shopping for swimwear, at Rip Curl's expense. At a beachfront store, Bethany and Alana encounter a fuming Malina, who boasts that she's going to beat Bethany at the next surfing regionals competition. Malina goes as far as to say that she'll be thinking about Bethany every day while training in the water. Bethany quips that Malina should focus on her surfing, as her skills could use some work. Malina lamely retorts, "We'll see," before walking away.
At the Hawaiian Island Regionals, Malina approaches Bethany at the sign-in desk and asks in a snarky tone if she's really going through with entering the competition, having lost her arm in a shark attack. Bethany states firmly that yes, she is going to compete. Just before the first heat begins, one of the race officials approaches Bethany and, in the hearing of Malina, offers the one-armed surfer a five-minute head start. Looking over at Malina, Bethany refuses the handicap. In the first heat, Malina beats Bethany to a wave and earns a 7.3 for her first ride. Bethany also catches a wave but loses control slightly, which costs her some points. In the next round, Alana cuts Malina off so that Bethany can take the next wave, which disqualifies Alana from the rest of the competition. Unfortunately, the next set of waves breaks Bethany's board, preventing her from advancing to the next heat. After she gets out of the water, she scolds Alana for dropping in on Malina like that. Alana says that Malina was being a jerk, but Bethany points out that at least Malina treats Bethany like she's real competition.
Against all odds, Bethany manages to qualify for the Rip Curl nationals. Just before the first set begins, Malina is seen posing for photographers, and one reporter mentions that Malina, who's won her last three contests, is clearly the athlete to beat. When Bethany shows up at the beach, all the photographers who were snapping pictures of Malina shift over to Bethany to take pictures of her instead. Jealously, Malina saunters over to Bethany and asks with a fake smile on her face what Bethany's doing there. She replies that she came to surf, and Malina ungraciously smirks that she hopes Bethany won't need to be towed in like last time. Surprisingly, Bethany thanks Malina for treating Bethany like real competition, never taking it easy on her despite her disability. Malina is left astonished, and the look on her face appears to imply that she is growing in respect for her rival.
In the final heat of the championships, Malina sprays Bethany in the face before snapping up a wave and carving out yet another high-scoring ride (9.25). In the audience, Bethany's brother Noah admits that Malina "is on fire today." When Alana takes a tumble, Malina picks up the wave and eeks out 9.5 score on her second ride. In order to prevent Bethany from catching the next wave, Malina paddle battles with Bethany, hoping to cut her off. Fortunately, Bethany is able to duck dive under Malina and catch a fantastic wave that nets her a 9.7 for her first ride of the heat.
Due to some bad luck, Bethany's final ride is disqualified because the judges deemed that she stood up after the final horn, giving Malina Birch the win. Malina is understandably ecstatic and jumps up and down with joy on the beach. At the awards ceremony, Bethany, who took fifth place, congratulates Malina on her win. In a touching moment, Malina invites Bethany onto the winner's podium and announces to the crowd, "I'd like to share this win with Bethany Hamilton because the judges may not have counted that last wave, but I did."