The answer is this: She's not happy.
One day after reps for Miley Cyrus and Liam Hemsworth confirmed that the young pair's engagement had ended, Hunger Games heartthrob Hemsworth was snapped locking lips with Mexican actress-singer Eiza Gonzalez.
"It's been hard for her," a source close to Cyrus tells People, on how the 20-year-old singer is reacting to the Hemsworth-Gonzalez hookup. "She can't believe he moved on so fast and so publicly."
Hemsworth and Gonzalez were spotted together in Vegas two nights in a row and later in Los Angeles.
The two are currently on opposite coasts with Hemsworth in Atlanta shooting the latest Hunger Games installment, and Gonzalez, a recent L.A. transplant, in Mexico to promote the Spanish language release of The Croods.
Miley, meanwhile, will return to the spotlight this weekend when she performs most likely, her new hit single "Wrecking Ball," at the iHeartRadio Music Festival in Las Vegas.
The star is reportedly "still deciding" what to do with the 3.5-carat Neil Lane engagement ring gifted to her by Hemsworth, who wanted Cyrus to remember the couple's happier memories together.
Luckily, Miley bird missed her former fiance- and now his new hookup- by one weekend.