He expected her to wait for him, but she's a modern woman and she can get home on her own. It's telling that she doesn't expect him to come back for her, or does she just not want to be there when he does?
While Washington is all a-twitter over two society climbers crashing the gates at an Obama soirée, in the grand sweep of history, it was a fairly minor event. No one was in danger, and no real harm was done, nobody got dosed with LSD.
When approached in isolation, drug policy almost always backfires, because it doesn't take into account the powerful economic, social, and cultural forces that also determine how and why Americans get high.