Sydney Sweeney became "best friends" with the person she plays in the new biopic Christy. In the biographical sports drama, the 28-year-old actress plays real-life boxer Christy Martin, who was "very involved" with the production and often on set during filming. While Martin's presence could have been a hindrance, Sweeney found her input very helpful, and the two became close friends. "She kind of became my best friend. Having her with us was a really powerful experience," Sweeney said during a post-screening Q&A at the Hamptons International Film Festival (HIFF) on Saturday, reports People. "I've never had the person who I'm portraying watch me. You're never really sure what they're thinking. But as it went on, I just wanted her there the entire time because I was able to study her and listen to her and have her thoughts and opinions there whenever I needed." The Euphoria star added that she tries to lose herself "completely" for her roles and not have any crossover with her personal life, but she "learned so much from Christy" which she applied to her own life. Elsewhere during the Q&A, the Anyone But You star shared how she physically prepared for the role for three months before production. "Every morning I would weight train for an hour, then I would go and do boxing for three hours, and then another hour of weight training at night," she divulged. "I did that every single day for three months, with a nutritionist, so eating a bunch of food and protein shakes and supplements. I, in that span of time, gained, like, 35 pounds." For her performance in the biopic, Sweeney was presented with the festival's Achievement in Acting award.