I believe the first time the Norwegian press pictured AND named Sonja was in September 1967 when a Norwegian magazine titled "Skal Harald få sin Sonja?" = "Should Harald get his Sonja?" and invited readers to participate in a poll about whether they should be allowed to marry.
She was pictured and named in the foreign press before that, but the Norwegian press did not dare. There were, however, articles and debates about whether Harald should be allowed to marry a commoner that implicitly referred to Sonja, because of course "the commoner" they meant was her.
Some of the foreign press even followed her around, for instance when she was studying at the University of Oslo. So in that sense, she was known to the foreign press & also to the Norwegian press, though the latter did not dare publish their knowledge and didn't follow her.