Your usage is more traditionally correct. Typographers and writers agree that the use of exclamation marks (also referred to as ‘bang’ or ‘screamer’) should be done sparingly.

But with so much informal (digital) communication, it’s taken on a new life as an indicator of friendliness.

Unlike the Germans, who have international government agreements that change the rules of their written language, English simply evolves with the next crop of teenage whims.

Which may be another way of saying that while you are correct, your wife is more hip.