Her being torn between the Crystal Gems and Yellow Diamond might not work, since she now seems pretty loyal to her.

Plus, I really hope it doesn't come down to "The minor-badguy doesn't want to help the good guys, villain does something that hurts/betrays minor-badguy, minor badguy joins good guys and that holds the secret to beating the villain."

It's really cliched and I think they can do far better than that.

That sound plausible. I hope it happens, especially the redemption part!