This drawing of Amethyst is really good!
the shading, lighting really stand out (in a good way)
Though there are 2 things I want to point out so I can help you improve :3
1) The fingers on Amethyst are very big an it's hard to tell that they are making a peace sign. It took me a moment to figure out what she was doing with her hand. I suck at drawing hands, so what do I know? XD
2) I (personally) think that the whip spikes need more dimension. One way I was thinking on helping this is adding lines to show that the spikes are more diamond shaped.
But besides those two (very) minor things, I think this is an AMAZING drawing! Great job! I hope you keep on improving and I love your Style!! (Brb I'm going to watch you now :3)