Hi Blackdrazon, welcome here :)

The small highlights make it look very plasticy, very glossy, there is definitely room for improvement!

Are you making versions facing the side too, and do you wish to mirror those so you only need to make one direction? In that case you can not use any side directional lightning, just top light. This is what you usually see in this kind sprites.

If you're only making these or are willing to draw two versions for the sides, the diagonal light is fine.

Her breasts seem a bit low to me, elbow height :o

Now as for top lighting, light would hit all areas that face the sky. Shoulders, top of chest, top of head, maybe forearms, and that's it.
Light reflecting from the surroundings can light up the rest of the character, but probably a bit less in creases and folds such as between the arms and the body, between the legs, and also any surface that faces downwards. Some body parts might also cast a small shadow, depending on the exact position of the light.

Does that help a bit?

Thank you both!  I'm probably going to have to re-measure some proportions. The camera is supposed to be at an angle, but that was a risky move to begin with and obviously I made mistakes.  Maybe I'll just use a traditional perspective for the time being, since I'm not sure I'm up to the skill level required for perspective art, and try it again for some other project when I'm more developed.

While this sprite doesn't require alternate left and right sprites, I may be using asymmetric sprites in the future.  Still, if it's traditional to do top-down, that's no skin off my back, I think I'll do that.

I'll see what I can do to improve and/or redraw and will hopefully post the updated product in a few days!