Would another correct answer be: "Flickan äter paprika"
Most likely not, since the course primarily uses American English, and they call it "bell pepper" or "sweet pepper".
After the boy who eats salt, that escalated quickly
Although not technically incorrect it is uncommon to say "eat" salt and pepper. More commonly we would say "take" salt and pepper.
It's not exactly common in Swedish, either. I mean, how often do you encounter someone actually eating pepper? This sentence means there's some girl actually snacking on pepper, not just adding it to her food.
Damn.. she's a badass..
This seems to me missing an article? Why not en peppar. I know it´s the same in Engelska too...
It's just pepper in general, not a specific amount. Plus, peppar is a mass noun in Swedish. It'd be like saying "the girl eats a cinnamon".