Hasn't anypony else read the book titled "Sunset Shimmer's Time to Shine" besides me? If not,I would recommend doing so
because I think it answers this question about what Sunset's element of Harmony might be. And the end of Rainbow Rocks may
support it, like when Sunset is trying to get Angel down from whatever it was that he was sitting on and Bulk Biceps came up
behind her and helpfully boosted her up on his shoulder so she better reach Angel better than her jumping up and down did.