I think you can get away with it. I wouldn't do it in a formal room or even my master, but for the girls' room, which will probably change in a few years anyway, I think it is fine and doesn't look bad at all.

With my children I've found that they tend to focus on wanting a particular wall color, but have difficulty envisioning the entire look and how one choice (bedding) impacts another (wall color). What has worked for me is to show them pictures until we choose an inspiration room. Pottery Barn Kids and Teen are a great source and they even list their wall colors on the website. I did a black&white & turquoise room for my older DD about 4-years ago and it still works. It's a classic look as is B&W & pink. I agree you can go many different ways with it; a Parisian theme or fun and bold. I try to work in the bolder colors with easy to change accents like pillows, etc. My DD turned 18 yesterday and has the B&W dotted bedding; but a friend of mine used that same bedding for her then 9-year-old and paired it up with pink walls and fluffy pink pillows. If you put the black in the bedding then your DD may agree to not doing the black accent wall (which I would try to discourage). If you have hardwood floors, then a fun and colorful rug is another place to bring in color. If your DD wants more black in her room, add in decorative black frames. Show her how to use black accents without painting the wall black.

Years ago I made dress up clothes for my niece and it was so much fun. She was about 6 and I bought a simple dress pattern in a size 10 or 12 so she could wear them for a long time. I made two dresses so she and a friend could play, varying the colors, sleeves and necklines, but made both with full, twirly skirts. Then I made simple stoles and scarves, bought some cheap bead necklaces and jewelry. I used swishy, taffeta type fabric that was not expensive, one dress was aqua blue and the other burgundy. Maybe you could find some hats at Goodwill or a thrift store - hats are such fun.

Depending upon her age, you could ask your daughter and follow her preference for her room. If the issue for you is the visual of it rather than spacing: With curtains on the window that hide the side window frames, you couldn't tell that wall behind the headboard is not as wide as the headboard. That might help the visual vibe. If you like the no curtain open window look, you could use both sheers and a pair of drape panels for each window and only cover the side window frames, leaving the shears in the middle to "cover" the window itself. Alternately, you could use a double rod and have the sheers on the inner rod and have the option to leave the curtains or drapes open or closed. You might also consider a different option: Change the bed to a metal frame (with wheels) -- without any headboard or foot board -- and use the window to the right of the chest of drawers as a headboard -- leaving the other windows unadorned, use curtains to create a theme at the head of the bed that represents your daughter's current interest.