I have the same problem, it is actually high levels of histamine in beer and wine, especially wine. Alcohol has a duel effect of disabling the enzyme in the stomach that breaks down histamine, and if you eat a meal high in histamine like beer and pizza, it can actually make me pretty sick.
Histamine is partly responsibly for nighttime wakefulness, just the same as an anti-histamine like benedryl makes you drowsy. She should stick to vodka and try not to eat too much when drinking, mostly breads and fatty food, but definitely not cheese or meat. If I follow this when I drink I feel 100x better.
Incase you missed it, vodka is amazing, make your gf some screwdrivers or whatever mixed drinks and see if it is better.