I suppose you haven't finished the book yet, as it's said in the text:
Smilla's parents (Danish father, Greenlandic mother) picked the Greenlandic name "Millaaraq", added an S so it became "Smillaaraq", which is "Smilla" for short, which sounds very much like the Danish word "smile" (pronounced "smee-leh") meaning "smile". So the name Smilla means something like "smiling". Unfortunately there's no meaning given for the original Greenlandic name "Millaaraq" :(
Have fun with the book! It's one of my favourites!