So, an idea for an episode: they kind of need to address the whole "Pink Diamond OWNED Spinel" thing at some point. Because Spinel needs to learn that she is her own person and that it's not okay for someone to own someone else. Like I can just imagine at some point she introduces herself as "Pink Diamon's Spinel", someone asks if that's the name of her planet or city or something, and she goes "No silly, she's my owner!" Cue awkward silence as Wander and Sylvia have to finally address it.
Now, Spinel had a bit of a different view of her relationship to Pink than most gems, she saw herself more as Pink's best friend than as her possession, but still acknowledges that she belonged to Pink. All she wanted was to make Pink happy, but she never thought that Pink would use or abuse her, she thought that they were genuinely friends.
That doesn't take away from the fact that there was still an extremely present power dynamic at play. It's still technically slavery, and slavery might be a bit of an intense subject to approach for an episode of Wander Over Yonder, plus it would be a little too on the nose, I mean the moral would be 'slavery bad'. So instead of just slavery it would be an episode that goes into unbalanced power dynamics in general. Spinel waits to be told what to do when it comes to serious situations, and hardly ever stands up for herself, because she's not used to making choices as a fully individual person. She was either with Pink, or completely alone.
Spinel's tendency to look to them for approval or to wonder what Pink would want her to do starts to concern Wander and Sylvia, and I feel like the episode would consist of a lot of them trying to walk her through situations to get her to think for herself in a way that isn't just coming up with a new game to play. It probably wouldn't work very well for a while, because she's still just doing what she thinks they would approve of. I feel like there would be a very important heart-to-heart between Spinel and Sylvia about how sometimes you need to do what's best for you, because if you only think about another person all the time, you're just going to get hurt. Spinel thinks about this and how Sylvia is always risking her own safety to try and help Wander all the time, and she frowns.
Meanwhile, Wander's approach is a little stranger, because he's trying to convince Spinel that she should think about more people than just one and try to help everyone she can. This is something that works for Wander and that he believes is genuinely helpful, but it can also be very harmful to him, which is one reason why he needs Sylvia to balance him out.
So I feel like a lot of it is Spinel looking between Wander and Sylvia's different approaches and having to figure out for herself what she wants, because thinking about yourself too much is bad, but so is only focusing on one person or focusing on everyone at once. The only thing Spinel wants is friendship, and to make Pink smile, But her experience in the garden changed her; she doesn't want to get hurt like that ever again. Plus, she wants to make her new friends smile just as much as Pink.
I do feel like this episode wouldn't completely resolve her feelings and she would have to meet Dominator later on to truly start her course of pursuing her own interests in a way that benefits her just as much as it benefits the people around her. It would be a rough track but it could get her mind to a much better place.