I'm also wondering how you are supposed to declare something like this. They don't pass out those customs forms on flights from Europe anymore, you just go through immigration and the officer asks whatever questions they feel like. In my case the only question was "did you buy anything".
> Then, as she headed toward the baggage claim, a Border Patrol officer approached her and asked to search her suitcase.
I'm sure there is something she was supposed to do if her lawyer is acknowledging she violated some regulation, I just have no idea what it would be.
If it's done on paper, this is done at the passport check, before you've picked up your checked luggage, and well before picking a customs lane.
I've certainly been randomly chosen for a screening, and when that happened, a customs agent went up to me (deliberately) shortly after I got my luggage. I forget why, but they have flags for suspicious behavior. I think it might have been because I came back with one more bag than I left with, or some intermediate destination.
There are also, in some airports, customs dogs sniffing things between luggage pickup and customs who can also flag for screens.
So none of this sounds too unusual to me, except for the final step: being shipped off to a detention center. I've never brought in anything improper, but I know people who came to the US with illicit food. The outcome was:
1) A rather serious fine
2) Being screened literally every time they passed into the US
The second was more obnoxious. Every time they came into the US for at least the next half-decade, customs would unpack their bags.