This slows the absorption of alcohol. Fats and carbohydrates are best for slowing absorption. Sugars intake prevents hang-overs. Cakes and pastries are the party food that has lots of all three. The water thing.
Dehydration is a big part of hang-overs.
Combat it while you are drinking. Intersperse the measily ration of drinks a woman has, with water-based drinks. Try to avoid ones with caffeine and acids. Depends on how easily upset the woman's stomach gets. If she has a weak stomach, skips the bubbles.