Your colour choices ended up very similar to mine - that's fine if that's what you want, but experiment with higher/lower contrast in value and hue, perhaps there's a look you'll like more. Remember that you can also shift the hues in different directions. I shifted my lights towards yellow and shadows towards blue, which is very common, especially if you want to give the feeling of being outside on a sunny day (sunny highlights, sky-blue ambient light filling the shadows), but that's hardly the only good lighting situation around.
The shirt collar looks good. In my edit I tweaked the collar shape a little to make the shirt look more like it's resting on a turned body, I recommend also trying that - not by copying my edit, but by looking at references (including the way shirt collars rest on your own body!) and applying that.
Her collarbones are too high up - something I didn't try to fix in my edit. If you struggle with them, you could safely leave them out - in a relaxed pose like this, they're not very prominent on most people. If you want to rise to the challenge, there should be plenty of reference online if you look up "collar bones". They connect to the shoulders, but they slope down, so near the middle they're noticeably lower than the shoulders. Yours are drawn higher than the shoulders.
If you move/remove the collarbones, you may find your next shadow looks strangely flat. You could suggest a bit more of the neck anatomy just with minor changes to the shadow/light boundary. There's no need to go very detailed with the neck anatomy, unless you want her to look sinewy.
Her headphone band looks very voluminous and round because it has a pixel of shadow, a pixel of midtone, and a pixel of highlight. Most headphone straps are flat, which means one colour (the colour of the top surface of the band) will dominate. You might not even have room for the others, and that's fine. You may be able to fit one colour as the shadow, and you can use the shadow it casts on the hair to give it volume without making it look round.
There are some areas with noticeable banding, such as where her skin-shadow lines up with the hair, on the headphone strap, and in the top left portion of her hair (the latter was in my edit too).
