The overall structure and tonal composition looks pretty solid so far.
The chin looks a bit wonky because the value transition is so abrupt–almost hard-edged, which gives the impression that the chin has two distinct planes, with the middle being a sharp angle. Obviously, that’s not how the chin is supposed to look.
Also, the way you rendered the form for the chin, makes it look like it’s just jutting out from her face, and there’s a distinct round-shaped parameter at the top separating her chin from her face. Again, that’s not how the chin is supposed to look.
There’s also this sliver of lighter value that reaches from the bottom of the chin and heading towards the hinge of the jaw. That thin sliver of lighter value doesn’t make any sense because it’s so isolated and there’s nothing to explain why it exists, when we don’t see on on the rest of her jawline.