So far the character's art is ok.
But I think you rely too much on the AI to do all the job.
Witch trainer uses a doll, on which clothes, facial expression, etc are added.
The fact you use the AI to render the whole character is limiting and will be even more down the road.
I think you should rend the doll and the accessories separately.
OR, use inpainting instead of a whole new prompt or img2img. When Snape shows her breasts, her clothes and thighs completely change. Only her arms and torso should.
Also, when you do your handmade changes, pay attention to the hands. Snape has 5 fingers. We should only see 4 when her arms are crossed.
I was going to say you should try to create the backgrounds with AI too, but I tried for the past 20min, and... yup, it's harder than I thought.
Good luck with your project.