The total number of oranges in all the trees before Dulce picked any is 8 trees * 200 oranges/tree = <<8*200=1600>>1600 oranges.
If each orange tree has 200 oranges, and Dulce picks 2/5 of each tree's oranges, she picks 2/5 * 200 oranges = <<2/5*200=80>>80 oranges.
Since the total number of orange trees is eight, Dulce picked 8 trees * 80 oranges/tree = <<8*80=640>>640 oranges from all the trees.
After picking 640 oranges from the trees, the total number of oranges remaining became 1600 oranges - 640 oranges = 960 oranges.
#### 960