carry an empty glass with you, and when they pester you, hand them the glass. They'll see it coming for them and the instinct will be to accept it. You can then say thank you to them for taking your glass away - it was a martini.
This should puzzle them long enough for you to find another corner, or a group of people / your friend, and surround yourself with protective others.
Incidently, once the happy couple leaves, you're socially free to leave too.