A few thoughts on the posing.....
Try having her turn her left shoulder slightly away from the camera (30-45° from lens axis). Currently, the pose is adding some tension. Also by this slight turn, it will give her an opportunity to not have to put her eyeballs in the corner of her eyesockets. A bit of white on either side of the iris is preferred. Otherwise, you get of a manic look.
If she is seated, try having her sit on her hip (near camera) rather than flat on her bottom. Additionally, a small footrest (4-8" - known as an apple crate) for her far camera foot will automatically give a new, fresh and more dynamic presence to the pose. A posing stand (anything out of frame will do) for her to rest her elbow upon will also change the dynamics because she will be leaning forward to the camera.
Smiling, happy, toothy expressions are not always necessary for portraiture.
Have a look at this posing tutorial.
The Rules Of Good Portraiture
I had more thoughts written down, but for some reason my 'puter decided to close the browser as I was hunting that tutorial. If it comes back to me, I'll add later.