First as far as the note, I would not assume that the individuals responsible are foreign or domestic based on the content. Something as simple as Google Translate can provide pretty good obfuscation, if you are fluent in Norwegian even better (I however am wholly unfamiliar with the language so will use a different example)

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Original English text: "Unless five million dollars are transferred to the following numbered account in seven days, I will capsize five tankers in the Ellingson fleet."

Google translation to German: "Wenn nicht innerhalb von sieben Tagen fünf Millionen Dollar auf das folgende Konto überwiesen werden, werde ich fünf Tanker der Ellingson-Flotte kentern."

Google translation back to English: "Unless five million dollars are transferred to the following account within seven days, I will capsize five tankers from the Ellingson fleet."

From there I can now manually change things with my fluency in the language "Unless million five dollars will be transferred to the following account within a time of seven days, will capsize five tankers from the Ellingson armada." and I've now drastically obfuscated any nationality/regionality/level of education that could be deduced from my request.

Or translate the German-English output to Spanish and back I get "Unless five million dollars are transferred to the next account within seven days, I will capsize five tankers from the Ellingson fleet." Which again gives me something that, at first glance, makes me seem like a non-native English speaker.

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>extreme confidence would be required to commit a crime of this nature in a foreign country.

I wouldn't say any more confidence than normal.

You could do the grab with 3-5 people with only a week on the ground prior to the grab if she regularly left the house.

Being Norway, and they're only worth about 200 million USD, I imagine she had no personal security detail, possibly a driver with minimal training (possibly just their assistant) and likely isn't instantly recognizable by the masses.

With no one on the inside you simply find a routine. Does she go to a social club regularly? Does she do philanthropic work somewhere? Does she like to do her own grocery shopping? Does she regularly visit one or more of her children? Were any schools in the area having any events being done by her grandchildren?

You figure out where she's going to be and when and it gets pretty easy. Intercept along the assumed route, ideally in a low-traffic area, or grab her.

Some quick research says they 'live a secluded lifestyle'. The population of their town isn't even 35k with at least 6500 of those being from other countries of origin (the majority of which from non-white nations) meaning someone with an accent/of a different race would not stick out whatsoever.

Given the size of the town I'm very willing to bed she does her own groceries, and other errands, and with some familiarity of Western and Northern Europeans they'll frequent the grocery/market weekly at a minimum due to generally smaller refrigerators/freezers as well as kitchens.

Casually approach her on the sidewalk with something appearing to be a firearm "Ma'am, remain calm and please come with us", fear and relatively casual guiding could have been enough to put her in a vehicle without a scene. From there you drive to any of the 1650 miles of sea boarder or to any number of fjords or bays and casually leave with her.

Could easily be domestic but there's zero readily available evidence here to suggest foreign kidnappers would have balked at the idea.