By Suzanne Zuckerman
March 25, 2013 12:00 PM

In their 3 ½ years together, Miley Cyrus and Liam Hemsworth have endured their share of ups and downs, including a split in 2010. “Miley and Liam have always had a very passionate relationship,” says a Cyrus source, who adds that her drastic makeover and their dueling careers have recently caused friction. “Their arguments this year have been ugly.” After Hemsworth, 23, was spotted out with Mad Men‘s January Jones, 35, on Feb. 23, “the cheating rumors pushed them farther apart,” says the source. Not only emotionally but physically: They were “arguing nonstop,” says the source, and Hemsworth took off for Australia on March 1 “so they could have a break.” Now, with 8,000 miles between them, Cyrus, 20, is left feeling “more sad than angry,” says the source, and she stepped out several times in L.A. without her engagement ring “to make Liam mad.” But this latest storm, according to Cyrus pal producer Adam Shankman, too shall pass. “I don’t know exactly how they weather it, but they do,” says Shankman, who has checked in with Cyrus and reports, “They’re fine.” Cyrus underlined that message on Twitter March 6: “I did not call off my wedding.” As Cyrus told PEOPLE in February, “Liam is the person I want to be with forever.” And that takes work. Says the source: “They are two very young people who are trying to find solutions to very grown-up issues.”