I tried the quick selection tool, but even though it seems to select the correct area, when I go to adjust the brightness or contrast, the area that changes isn't the foreground, but the full sweater that I don't want any darker.
- Your selection very likely semi-transparent selection areas. You could verify that by viewing the actual selection in Quick mask mode or enabling the respective channel in the channels palette. Based on your screenshot nobody can tell exactly what it looks like, but you need to loook into that and adjust your settings, use different selection methods and so on.
- Brightness/ Contrast is an unsuitable adjustment. You still have color in your shirt and table cloth and simply globalyl cranking up brightness will eradicate every detail. use Levels, Curves and Color Balance adjustments or simply desaturate the whites to remove the blue-ish tones.
- That being said, as far as the computer is concerned, white is white. Where no details were recorded, none will appear. You won't be able to recover any info in the blown-out areas that already are screaming white. You have killed them with teh flash.
the top of her dark hair blends into the dark background. Is there something I can try to improve that distinction?
Same as your other issue - you need to even out the overall contrast. There's enough distinction to create a quick selection e.g. with the magnetic lasso and slightly brighten the foreground with adjustments, using the color dodge/ burn tools to enhance the details in teh selection or duplicate the layer and mask it with the selction, then usie blending modes with tweaked opacity... Conversely, you might also already get a better image by desaturating the background so the gloomy and distracting yellow-ish tones are subdued.
Mylenium