Miley's former fiancé was spotted in a passionate embrace with actress and singer Eiza Gonzalez the day after their breakup was announced.
"She knows Liam has been seeing Eiza and it's been hard for her," a source close to the former Hannah Montana star told PEOPLE magazine. "She can't believe he moved on so fast and so publicly."
The handsome Hunger Games actor was spotted partying with the 23-year-old Mexican beauty at a VIP club in Las Vegas last weekend.
"They never left each other's sides," a source told Life & Style. "They were with a few people and spent a few minutes at the VIP DJ stage table. They then headed back to a more private VIP bungalow cabana near the pool ."
"They had drinks and talked in the bungalow. They left together with the rest of the group around 2 am," the insider added.
The pair were also seen the next day, meaning that 23-year-old Liam may be enjoying being single again – or maybe he is already off the market.
Spokespeople for both Miley and Liam confirmed the news on Monday that the couple had split after months of speculation.
They were last seen together in August for the LA premiere of actor Liam's latest film Paranoia.
Miley, 20, and 23-year-old Liam met on the set of The Last Song in 2010 and got engaged in May last year.