Hun ankommer i en bil, men hun ankommer til Danmark. Ankomme i Danmark er absurd!
Continental drift gone mad.
Some natives say "i", but I agree it sounds wrong.
'She arrives in Denmark next month' is a perfectly good translation of this and should have been accepted.
In English you can, just like in Danish, use the present to imply the future. Particularly with the word arrive. When will your aunt arrive.? She arrives next week etc
is a perfectly acceptable English sentence
"She is to arrive in Denmark next month" would also be acceptable in English.
Man ankommer til ikke i
Same goes for "she will arrive ..."
"She is going to arrive TO Denmark next month " is also wrong ?