• Your drawing ability is right on.
• The figure is well placed in the picture plane.
• The line direction in the drapes in the background helps keep our eye in the picture as well as give us an opportunity to create the value contrast we needed.
• You didn't crop her body at any of the joints; that would be a no-no.

I feel that a black and white drawing must contain a richness in value which can only be achieved by strong value contrasts. It will be helpful to think in 6 values.

See this chart below:

In your original drawing we have predominant light gray and middle tone. However we need a darker value to create more light light. Light against dark, dark against light-these are two of the most effective means you have of riveting the viewer's attention.

The value scale above - black and white with four distinct grays in between - offers a full range of values with a manageable number of different tones.