My parents got divorced 2 years ago and my mom met and started dating this guy from North Dakota, U.S. We're from Romania. Next month she's taking me to the U.S. for the first time to spend winter vacation with her and her boyfriend. Honestly never heard of North Dakota before... seems to be a not much talked about state.
And compare it to cities you're familiar with to get an idea of the size to expect. The west side of the state is dominated by oil wells, don't know if it's still like this but you used to see flare stacks (giant flames of venting gas) basically everywhere out there.
The winter are rough, it gets very cold due to the Polar jet stream dropping south of it. Also the majority of it is flat open plains so it's very windy and the snow drifts really high and roads often become impassable for a while.
https://en.m.wikipedia.org/wiki/Climate_of_North_Dakota
In my experience the people are a mixed bag just like anywhere else. Some are great some are awful. A lot of the folks I met were super into outdoor activities like hunting and fishing. I would be careful if you're near or on a Native American Reservation. I wouldn't wander around alone as folks tend to be less friendly to people that aren't a part of their community, they're a historically marginalized population and the recent oil and gas exploration hasn't done them many favors. They also have their own system of law outside the United States Federal Government, and it can be confusing. (If you're with someone local you're fine.)
Lastly Romance Scams are a thing and human trafficking does happen. Before she goes off to the middle of nowhere with someone she should let someone who can contact authorities know, and give them as many details about the person including social media links and emails as possible:
https://attorneygeneral.nd.gov/consumer-resources/common-scams/
In the US you can call 911 to get emergency services anytime and anywhere. North Dakota has its own human trafficking task force:
https://www.ndhttf.org/
North Dakota is probably one of the coldest states in the country during winter. I don't know what it's like in Romania, but be prepared. The state is also landlocked and pretty much completely flat. There are lakes to boat in during the summer which is cool but I don't know what type of winter activities there really are unless you're into curling.