updated 04/06/2010 AT 2:00 PM ET
•originally published 04/07/2010 AT 9:15 AM ET
Last Saturday the two flew to Sin City together where the Hills star was scheduled to host a pool party at MGM Grand’s West Republic. Cut to the actual bash – and Cabrera was nowhere to be seen. Patridge wasn’t too chatty either, avoiding the media and barely posing for photos at the event.
That night Patridge, 24, dined at Craftsteak with a group of friends. Again she was without Cabrera, who spent his night partying at The Bank and at Pure Nightclub.
“He seemed bitter,” an onlooker, who saw Cabrera, 27, that night told PEOPLE.
First linked in January, the two have had a bit of a bumpy road – spatting in public and at various events around Los Angeles in recent weeks.