A few more pictures of the room currently

Before Pics

It's looking lovely! Adding some colorful/solid accent pillows could help complete the bed. Maybe some solid green or yellow throw pillows--or add some texture by adding a long-hair fur pillow like this one from West Elm: http://www.westelm.com/products/7127616/?catalogId=15&bnrid=3917700&cm_ven=AfCompShop&cm_cat=TheFind&cm_pla=GAN&cm_ite=Std

Also, a simple rug could always help update appearance of the carpet/floor.

I like the furniture. I think a bohemian or gypsy direction may be a good idea.
Or perhaps something like the second photo using navy blue as your pop of color.

Maybe switching the desk and the armoire. I like the furniture except the brown table..paint white or replace. Yes, a larger lamp. Some the art work does not look like a teen would like..maybe some vintage posters about things she likes..travel, sports, fashion..............(large reasonably priced selection at zazzle and other sites)

Paint the wood table to match the other white pieces. Change the art to something fresher. I would change the drapes they look too dense.

You've done a wonderful job so far. I like the "really good day" picture, but not its placement. Find some fun art that complements it and make a gallery wall over the seating by the entry door.

I love the headboard and bedding! I don't think every piece of furniture needs to be matchy-matchy, but the one wood side table stands out a little. Maybe make it stand out a lot in a bright color pulled from the bedding? If you're not going to pull out the carpet, a big area rug can add color and style (and detract from the bright blue shag!). I agree that the drapes are WAY too heavy for the room. You can get lighter fabric in a cool pattern either lined with blackout material or back it yourself for light control. She needs tons of art on the walls - group all the little tiny pieces she has in a gallery wall over the bed or vanity, and get some bigger canvases or posters for the rest of the room. Maybe even a temporary wallpaper accent wall? They're easy to put up and take down, like big stickers, so it's not the commitment and work of regular wallpaper, but looks fancier than paint.

If the door to her room is on the left of the bed, have you thought of turning the bed around to sit between the windows, where the low dresser is? I think this will have a better traffic flow. Her cute blue chair could then go between the two windows in the corner where the armoire is blocking the view - this area will be good for reading, or piling clothes. Armoire can move to couch area. Low dresser where the headboard was. Sofa could go at the bottom of the bed. And the desk could stay where it is.
The pillows on the bed could go on the sofa, to bring the blue colour, lighten the look, and be comfy. I think they are too similar in pattern size to complement the bed.
I really like the mirror, bedding, and your furniture. Anthropologie has great looks for teens.
A DIY project could be making a bulletin board for the desk area - ribbon holders, chalk paint, cork for pins.
Having fun with it is the first step!

I would definitely paint the wood table a high gloss bright color, perhaps pick up the chartreuse in the bedding? Adding to the gallery wall is a great idea, maybe frame some really cool photos from her/her friends Instagram accounts? Also, a framed chalkboard (which you can make pretty easily), would be great above the desk. And, consider changing out drawer knobs and pulls to something bolder! Good luck. It looks great. What a fun project for the two of you!

The blue cushion/settee looks like it would be perfect on a platform made from pallets (check how-tos on Pinterest. Paint wood white to match furniture. Place the 2throw pillows from bed on this "sofa". Larger lamp, perhaps one on the dresser also. Chalk/bulletin board above desk. Put chair in corner where armoire is currently. Lighter print drapes. (Do you still have the blinds on them?). If you leave the bed where it is, paint accent wall behind it. Arrange art on this wall, as indicated earlier. I like using the chartreuse or green from the throw pillows for bold accent colors. Either paint the brown side table white, or get rid of it. I saw a soft ruffled satiny pillow @pier one today, it is so soft, you will want to touch it constantly. I would try the green or deep blue as throw pillow on the bed.

Great job so far. It's going to be a fabulous room. I added a gray accent wall behind the bed, painted the bedside table and added a lamp and artwork. Have fun!