Dear Miss Manners: While on a group tour abroad, I invited three travel companions to share a bottle of wine, and they accepted. However, when the waiter poured, one lady opted for a soda instead. Am I required to pay for her drink? I did, but what if she had chosen a cocktail instead?

Gentle Reader: "Obligation" is a strong term. It’s reasonable to assume that you were treating your companions to a round of drinks, not just that particular bottle. Your friend’s deviation from the original plan isn’t as significant as you believe. Paying for her soda, which she might have ordered for various reasons—perhaps she had a pending work call or is sensitive to that type of wine—was a gracious act.

If she had wanted a cocktail, it would have still been considerate to cover it, though she might have felt inclined to contribute to the higher cost. Ultimately, the cost of accommodating her choice is trivial compared to the value of maintaining amicable relations and avoiding grudges. Trust that they will reciprocate your generosity during the next round.