Selina & Open
This was not her native environment, not the world she had been born into, not by a long shot, but Selina Kyle blended into it seamlessly. Long practice ensured it. And even if some of these parties were dreadfully boring, being interested wasn't why most of these people were here. Networking, hobknobbing, gossiping, there were a thousand different variations on why people were nearly required to come to events like this, whether or not they cared about the pale excuse for a party that started the whole mess. (A bombed country, someone's birthday, the wedding anniversary of a couple that probably wasn't even speaking anymore.)
The new Selina Kyle came for those reasons, at least ostensibly. But she also came for the food (usually stupendous), the drinks (usually better) and the sheer, satisfying fun of putting one over on the rich and powerful.
So she'd come out to Metropolis, put on a slinky dress and some diamonds (not stolen, but certainly bought with ill-gotten gains), and joined the wealthy and concerned at the Wayne benefit gala. She was drifting through the crowd, meeting and greeting, playing the part with dedication. Part of the impetus to come might have been to case the wealthy people of Metropolis, for a change; another part was probably to snoop on Bruce Wayne, and figure out what he was up to. And the deception was fun; another part of the fun was the collection of oyster forks she was amassing in convenient places in her dress and purse. If she couldn't clean the caterer out of every oyster fork in their inventory by the end of the evening, well, she was no longer a master thief.