What I ended up is the selection you see on the top left. If you look at the edge of her face, you'll notice that the selection line is travelling at the middle of the inks, this is because by using the "Flats" Channel, I was able to unselect elements surrounding her face by using the Magic Wand Tool (W) . I also removed the selection surrounding her eyes to avoid coloring over it.

Now, remember that overlapped selection on her nose? I wanted that specific area to be more crisp than the rest, so what i'll do is use the Polygonal Lasso Tool (L) , set the Feather to about 4 px. By holding the ALT button while clicking on the selection, you can subtract the unwanted area off (the red line on the left image indicates the selection I made using the Lasso Tool).

When I have the mask I wanted, I hit Ctrl+H (Win) or Apple+H (Mac) to hide those squiggling lines and start shading again with the Brush Tool.

The result is the image you see on the left.

Relatively, I'll go and repeat the process on the other side of her face to add shadows to contour