Honestly.

"Unless you care to change the plan I had when I boarded the plane," you tell her, laughing lightly since you know you're quite likely to be rejected.

"I might care to," she answers, "except that you no doubt noticed I have a fiancee, and we care to stay with each other and nobody else."

You say nothing, simply looking straight ahead and nodding.

"However," she continues, "I am a long-time resident of 'The City That Never Sleeps', and if you'd like, I could introduce you to some single friends with whom you might share an interest in not-sleeping together."