She said they use a "traffic light system" to monitor passengers. If you're "green", they'll keep serving you, if you're "yellow" they'll slow you down.
When you're "red" - glassy-eyed, unsteady and slurring - they'll stop giving you grog.
"It's a red flag if someone is getting up to use the lavatory more often than normal," she said.
"Or when they start pulling seemingly sly tricks.
"People often think they can sneak in extra drinks by requesting them from a different flight attendant each time. Actually, you're just drawing more attention to yourself."
However, telling someone to stop can get awkward.
"It's embarrassing for all involved," she admitted.
"I quite often just pretend I haven't noticed the passenger who's waving me down for another drink until they give up. That or I just 'forget' their order."