-There is only 2 shades of color on her hair.
Try using the 3 color method. Light, medium and Dark
This can be applied to her skin, clothes etc.
-Not enough shading on certain points like under her neck, her arms etc.
-Where is the light source coming from? Pinpoint the light source and use that as a compass to find where too shade. Is it behind her? Is it exclusively on her card? How about on top?
When coloring always take a small break and look at it from a distance. That way you can see where you are and how to fix areas that need attention.
-Look at the reference can help guide you on what colors you need