The University of Southern California junior was photographed partying with friends in Cabo San Lucas, Mexico, Sunday. Schwarzenegger is flying solo during spring break, as Cyrus opted to stay home. On Monday, The Daily Mail published pictures of a bikini-clad Kappa Kappa Gamma sorority sister with her arms wrapped around Schwarzenegger's neck. The U.K. tabloid described the exchange as a "loving embrace." It also argued that Schwarzenegger and his pal looked "worse for wear as they strolled along the beach arm-in-arm."
TMZ also published the photos and argued that "'friends' don't usually do body shots off one another." The site added, "Then again, when Miley is your girlfriend, something like this is probably no big deal."
Schwarzenegger immediately denied that implication that he acted inappropriately. "Omg. It's one of my best friends girlfriend..." he tweeted Monday afternoon. "Would NEVER do anything against my GF."
In another tweet, Schwarzenegger wrote, "Girls have guy friends and guys have friends that are girls..."
"They are not together at all—just friends," a source tells E! News. "USC invades Cabo during spring break."
Cyrus, meanwhile, has yet to publicly comment on the paparazzi pictures.
That being said, a source recently told E! News that Schwarzenegger, 21, and Cyrus, 22, are "super serious." Schwarzenegger's mother, Maria Shriver, "really likes Miley and thinks she is a terrific girl." His older sister, Katherine Schwarzenegger, agrees. "I think they're adorable," she told Extra last week. "If my brother's happy, I'm happy and that's all that matters to me. You just want your sibling to be happy, if they're with someone who makes them happy and in a happy healthy relationship then I'm happy."
In a 2011 Details profile, Schwarzenegger named celebrity friends Kendall Jenner and Selena Gomez as "girls for the future," adding, "My eye, though, is set on Miley." At the time, however, Cyrus was dating Liam Hemsworth. The Last Song co-stars got engaged in 2012, but they called it quits in the fall of 2013. Schwarzenegger split from his high school sweetheart Tootsie Burns in 2014, and several months after they broke up, the Grown Ups 2 actor took his relationship with Cyrus public during a USC football game.
—Reporting by Sara Kitnick