Ollie hadn't been invited. He'd just happened into the same bar, and it wasn't hard to spot Dinah and Zee once he was there. Although, once he spotted them, he seriously considered sneaking out before they saw him. Dinah? And Zatana? Together? He'd be doomed.
And then he remembered that he was supposed to be the cool cat, and kicked himself in the pants, sauntering over as if he hadn't a care in the world. "Hello, ladies."