"She is down on the floor underneath."
Translation:Hon är nere på våningen under.
Nere is down (location) like ’He is down there’, ner/ned means motion down like ’I am going down the stairs’. Ned is the more formal and written variant of the two but they mean the same thing. Nedför/nerför is sort of downwards alongside something. You could also say Han gick nedför trappan for ’He went down the stairs’ since you’re walking along the stairs.