I think the blank expression hurts it a bit too. I don't know anything about the character, but maybe a slight turn up at the edge of the mouth, or a little expression in the eyelids or eyebrows? Even a stoic, regal expression like you may be going for has a little variation in it, all the features are just so level and even.
Lastly, the legs are very confusing, I can't tell where her knees are supposed to be. (gravity would show the fabric shaping around them) . The whole dress pinches in just under where her hips are, and where I presume her thighs would be making it a little shapeless and looks like she is floating above the chair rather than having contact with it.
Hope this helps.