The colors here are strikingly beautiful, and the way her hair fades softly into the background is lovely. She's got a certain type of old school film glamor. Her expression is confident bordering on smug, and it's easy to imagine her as a romantic lead. Technically the work on the hair and the fur at her throat are amazing, and your patience there must have been astounding. All that said, for improvement there are two different things that you might consider:
- Changing the composition. There isn't much to draw the eye, once you've seen the hair. Her face shows an intense character, there are beautiful details in the fur and the pearls at her throat, but my eyes aren't being lead there by the composition, I'm forcing them there to appreciate your technical prowess, since you asked for critique. A larger view of the whole character, or some larger background details, or a different crop could make the picture seem more alive.
- Add some brightness to the pearls. This would help draw the eye through the portrait, and would be another option from changing composition. The pearls are beautifully rendered right now, but you could have the option to glow in the same way the hair does, and pick up some unusual color, making them a bigger part of the piece, and work for the portrait, rather than act as a simple accessory.
Even so, this piece is gorgeous, and I love it.