Ah, just another thought I had from looking at some of the other pictures: I think the reason the edges look so "hard" is probably because the hair is really soft (whether the accessory was drawn or not). Once again, a blurring tool might work, or softer lines while drawing it might make it less "slappy," as I like to put it.
Wow! Her hair is AMAZING! She's very well done, and the details in her outfit are very well done: realistic, but not overbearing.
Just something I happened to notice: for some reason, her hair accesories don't look like they're naturally on her hair. It looks like you tried adding it on to her in Photoshop or a similar program (just a guess). I would perhaps recommend trying to soften the details on the hair accessories, especially around the edges, with a blurring tool. Not in excess, anyway, but just so that the edges don't jump out and slap the viewer in the face.
But then again, it's just a guess. If I'm wrong, feel free to slap me >.<