A seems the most right because if the girl is developing so is the setting because the girl is the setting
I have written a similar essay. Except it was multiple pieces completed by two different artists. I would say start with the intro, then write the similarities in the second paragraph, the differences in the second paragraph, and the conclusion. If you need more paragraphs to reach requirements then do this:
1. Intro: give brief background to artwork and artist and write thesis
2. Similarities in technique
3. Differences in technique
4. Similarities in emotion conveyed
5. Differences in emotion conveyed
6. Conclusion: summarize comparison and rephrase thesis.
*no idea if this answers your question*
