Being satisfied without being bad

Recently, I asked my wife if she would like another mojito, a delicious Cuban cocktail made of rum and limes. She replied to me: "I'm good." She meant, "No, thanks. I'm satisfied"; or, "No thanks. I'm effectively full." She did not mean to suggest that she is a decent person, or a well-behaved person, or even that she is in fine condition. (see below). Admittedly the odds favored my wife and many others using this perfectly useful word according to Project Gutenberg, (ranked number 98), yet, we are hopeful, under conditions other than rejecting a delicious cocktail.

Grammatically, when one says (as many today do say) "I'm good," they are literally arrogating to themselves high compliments of decency, being well-behaved, being moral, enjoyable, healthful (that is, good for your health...), even if their intent is an idiomatic "No thank you." My wife is certainly all of the virtues ascribed to "good," a fact that has well-complemented our partnership and my affection for her, but really, to reject a perfectly good drink while arrogating to yourself the virtues of "good," is not seemly, even if an accepted idiom.

I (subject) am (linking verb) good. (predicate adjective).

good: adj. excellent; pleasant; pleasurable; decent; valid; well-behaved; in fine condition, useful, healthful, beneficial, competent, skilled; positive; having admirable moral values

While we understand the idiomatic intent of my wife's response, some idioms I will not abide. "I'm good" is one such idiom. How about the simple: "I'm satisfied," or "I'm content." Literal meanings are not always to be avoided. The point: Do not use idioms as a shorthand always when a literal response will suffice. Sometimes, literalness is good. That is: useful and beneficial.