Does your daughter have any posters or art that she would like to display? That would be the first place to start since she is a teenager.

I would suggest adding a chair rail around the room. Then, paint the wall below the rail a very pale shade of the turquoise you have in the headboard and curtains, but light enough to make a significant contrast. Then, I would suggest you paint the wall above the chair rail white to go with the white furniture. If you want to be really bold, add white-painted crown molding around the ceiling/wall juncture and then paint the ceiling a turquoise that is between the lower wall color and the headboard color. To avoid plainness in the room, perhaps you find a white tone-on-tone leafy print wallpaper to put above the chair rail. It will give a subtle pattern without being too busy. An accent color like fuchsia or yellow will give added punch to the room and will be a fun color for your daughter.

I don't think the color of the walls are working. I would paint the headboard wall a deep chocolate brown. The other 3 walls the same color blue that is in the comforter/pillow.

Even though the blue sheers work, they are not having any impact. Consider a heavier weight fabric for more drama and contrast.

I was thinking to add an accent color like lime green to give it some punch. You can create an accent wall behind the bed with wallpaper, or paint. You can add a trio of mirrors, or mirrors in different sizes and place them randomly on the wall.