Translation:The girl's mind was full of stories.
To mean the subject History this sentence would read "Jentas sinn var fullt av historie".
I was a bit easy going on the details when I wrote my previous reply, "historie" meaning history almost never gets a plural ending (at least I can't think of any example where it would) so that is actually a way to separate them.
It's from a master "synonym" list Duo keeps, which affects all courses and cannot be overridden by course contributors. It equates "story" with "storey" and "floor", forgetting that it can be a bedtime story rather than the story of a building.
We've complained about this several times, but to no avail.
Just to confirm, or any Norwegians confused by this:
story (plural, stories), for bedtime story
storey (plural, storeys), for the floor of a building. (You might also see "stories" as the plural for "storey"; according to my dictionary that is technically correct [hence Duo's confusion], but I can't remember ever seeing it in use, and most people [in the UK, at least] would consider it wrong. I suggest sticking to "storeys".)
That sucks that you can't change it. Is there anything we can do to chivvy them up?