"Omission" is NOT a misrepresentation, and certainly not a material misrepresentation, if the person leaves as scheduled, or even later, but within the time granted. Again, it is not illegal to marry while in the USA. What's illegal is to overstay and what "may be perceived" as illegal "intent" is only applicable when adjusting status.
I'm not implying or otherwise saying your advice was to volunteer information. It's just that you were not CLEAR about what direct question, would necessitate mentioning the wedding. I've been clear. If you meant the same, then great. No disagreement here.
If asked for the purpose of her visit, "to visit my boyfriend" is currently still a truthful, concise answer, for next visit.