Gregory Michael

Just hours after Vienna Girardi moved her ass out of Jake Pavelka's home -- she was already partying with the man she was rumored to be hooking up with on the side ... Gregory Michael. Vienna and the "Greek" actor were dancing with each other -- hand-in-hand -- at the Reality Cares CHOC Children's…

Sources involved in the production of "The Bachelor" tell TMZ Jake Pavelka was the person who pulled the plug on his relationship with Vienna Girardi ... because he thought she was cheating. We're told Jake believed Vienna was "stepping out" with Gregory Michael -- an actor on the ABC Family show…