During the entire tutorial, it's selected around the lineart, so nothing goes out of the lines. The step is making a new layer, then color it with the darker/fade color to halfway through your body. Use the blur tool (I don't know what the density is, she didn't specify) and then blur the fade color all over.
Okay, You Know " Magic wand " It look likes magic stick. use that's Chick to Brown back then go to top of Bar " Selection " then if you see "Invert Selection " it inside the lines now you can color Inside No Outside!