Tip 1. When you draw out your picture try to avoid tell tale pencil/carbon lines showing through, notice the feint line to the right of the nose.
Tip 2. I am unsure if the hair is behind or over the ear, to correct this is easy. If you wish the hair to be behind then lighten the top of the era and darken the hair directly above it this will give you the impression that the hair falls behind the ear. If you want the hair to go over the top of the ear then place a shadow on the top of the ear directly below the hair.
My advice to Merce would be to keep doing what she is obviously good at and take little steps like the ones I have mentioned don’t go in for giant leaps. The ‘Two Children’ picture will be up soon for members and this lovely pastel pencil painting will help you with your understanding of portrait work more than any written or spoken words can do.