Technically speaking, the club owner who went by the name Hermia Dite had no reason to be there. For that matter, neither did Hermaphroditus, child of Aphrodite and Hermes. She wasn't rich, and he wasn't concerned about the environment. Not unusually so, anyway. He liked animals, but wasn't opposed to eating meat, and didn't want the world to drown in its own waste, but didn't go out of his way to help the environment. The most she did was use the subway and he had a recycling bin, but nothing beyond that. He certainly didn't do anything to decrease the waste she put out, only divert it.
The reason she was there had nothing to do with the cause itself, though he was unlikely to be alone in this. Hermaphroditus was the fusion of a child of Aphrodite and a nymph so caught up in her own lustful urges that she'd pounce on a boy she didn't even know and ultimately fuse with him rather than let him go.
Granted, the child of Aphrodite had been rather shy, but he was older now, and had been sharing a body with Salmacis for several millennia. So, when she came across an attractive, rather rich man named Mr. Stark, she flirted a bit, left out the whole part about her not being truly female, and soon found himself being the 'plus one' to this lovely gala.
The fact that the food would all be vegan certainly put a damper on the whole eating thing, but maybe if the chef was good enough he could actually make the food taste good despite that. Besides, if nothing else, it was his chance to show off the beautiful red dress Mr. Stark had bought her for the occasion.